MELTDOWN! Please help: advise needed

[RallyGSX]

Help! My engine had a meltdown, and I want to be sure I don't repeat the problem... Anyway, I'm working on building a rally car one step at a time, Maybe I got the steps in the wrong order, or I have to do them all at once...
Mods so far:
Ported 16G Turbo, 2g Manifold, 2 1/2 " Turbo Back, Manual Boost controll set at 14 lbs., K+N and Hacked Aircan
JE 9:1 pistons, JUN flywheel w/out balance shafts
I have a 255 fuel pump and denso 660 injectors
The car was tuned w/ a logger and at the Dyno w/SAFC

I own, but have NOT installed: FMIC, -6 Fuel line and AFPR, Fuel Pump rewire hardware, 3" Turbo Back, Ported Evo Manifold and O2 Housing , Ported head w/ O/S SS Valves, HKS 264/272 Cams...etc.

The motor started having lots of crankcase blowby (filled oil catchcan very quickly), ran about 10-15 degrees too warm, some steam vapor came out of catchcan, then it started hesitating whenever I hit the gas and was retired. Upon inspection the cylinders were full of gas, #1 and 2 were at 90 lbs compression, others were at 145. After the head was removed it was discovered #1 and 2 pistons started to vaporize... #1 was worse than #2. The block and head were not damaged, it seems that the pistons started burning, alum. particles could not be found...
My first thought was fuel delivery problems, but it's not developing serious HP at this time, (and has a recent fuel filter change): 216 SAE HP, 235 lb-ft SAE Torque at the wheel...
Did I kill my car w/ fuel starvation?
Any Advise would be GREATLY APPRECIATED!!!

 

[jott5555]

could have been detonation

 

[RallyGSX]

Yes, Detonation occured to me , but my TMO logger was reading 0-3 counts on the knock sensor...

 

[GTM]

Originally posted by RallyGSX
Help! My engine had a meltdown, and I want to be sure I don't repeat the problem...
...

The motor started having lots of crankcase blowby (filled oil catchcan very quickly), ran about 10-15 degrees too warm, some steam vapor came out of catchcan, then it started hesitating whenever I hit the gas and was retired.
...
The block and head were not damaged, it seems that the pistons started burning, alum. particles could not be found...

My first thought was fuel delivery problems, but it's not developing serious HP at this time, (and has a recent fuel filter change): 216 SAE HP, 235 lb-ft SAE Torque at the wheel...
Did I kill my car w/ fuel starvation?
Any Advise would be GREATLY APPRECIATED!!!

First, remember I don't own a DSM, it's my son's car which has no mods, timing may be 5deg advanced. It, during his ownership has always run on So. Ca. 87 octane gas. The few times it's pinged he and I have backed out of it.

I read some of these mods and don't have a clue what they are reported to do... I can make some guesses though.

Let's see if I can make some sense of what I do know. I've seen a couple dozen melt downs on carb engines only. In the early stages you won't find much trace of the aluminum though the top ring groove may show abnormal wear. Spark plugs will show some tell-tale spots. Exhaust valve seats will show some very fine dents.

I would hope you had the head pressure tested properly and hot tanked. This will remove a lot of scale build up in the water passages.

In your PM you mentioned having to drive at the 9000 foot altitude level though not the lower elevations. Off the top I'd be very suspicious of those 660 injectors are just not going to work for you since you can't get the air at 9000'. I've not thought about or done any math for the 14 psi boost.

So if you are running rich, you will have performance loss, you will over compensate by pressing harder to achieve the same speed making the engine work harder yet not going any faster for the number of calories (BTU) input but you have not increased the air flow over the radiator so the temp goes up in the thin air it can't exchange the same heat as at sealevel. Your gas milage must be awful.

So you need to use a smaller injector, here you are going to discuss this with someone who has experience. A service manager at the local dealership may be able to tell you what they have had to do for their customers in similar situations.

You with me so far? More to follow, just have to gel ideas.

Cheers,
GTM

 

[GTM]

Originally posted by RallyGSX
Yes, Detonation occured to me , but my TMO logger was reading 0-3 counts on the knock sensor...

Yes, detonation could have been a factor... BUT then why not ALL cylrs??? Once loosing compression on 1&2 your already rich condition became worse thus the wet condition of those 2 cylrs. I can't tell you how the knock sensor would respond before and after the problem. Hope you are rurnning ARP type studs.

I would suggest you need a pyrometer if you don't have one. A fuel pressure gauge so you know you have the needed pressure and not sometimes getting a lean (low pressure) condition when you back off the gas yet have all those excess combustables (carbon and fuel) built up. Kinda guessing here to explain what transpired so it doesn't happen again. And the sensor which tells you if you are running rich or lean... can't remember the name (see what happens when you get old) if you don't have it. Somebody help me out here.

O2 sensor malfunction??

You may need to have a larger fuel rail, you could go back to the stock injectors and monitor O2, pyrometer (EGT) and fuel pressure. while running the stock injectors. Increase the radiator and possibly oil cooler, and IC size again for the air flow rate at that altitude.

Perhaps you saw the head gasket water passage concern I started and this too may be an issue for you. Definately warrants more concern and it may prove to be you can't just open up all holes but only some to get better water flow. I have seen posts here where their have been discussions on why 1&2 or 3&4 will have certain problems but there wasn't any convincing conclusions from the participants. I have seen some picts of head cutaway sections where you could better see the water passages which would help in deciding how to best get the needed circulation. Wouldn't hurt my feelings if you were to match port the thermostat fittings and the head to get things smooth with no sharp edges. Water is 70x denser than air and has all the same problems as gas flow plus some.

BTW is that a 1G turbo block with the oilers? You could have a problem there on 1&2 being plugged. There is a good article by a pro builder on that oilling system which could be helpful. I had a point or 2 that I didn't agree with (and wrote them without response) but at least give it a good read for they did the research. Some people wont give you the time of day...

Kick some of this around, hopefully we will get some more input expecially with your mods.

Cheers,
GTM

 

[RallyGSX]

Thanks for the input, I may have a theory that ties it together.

As far as Detonation, maybe it was detonating just on #1 and #2 and the knock sensor did'nt pick it up for some reason...

My logger confirmed the O2 sensor was working, and occasionally the knock sensor would go up to 3 on a scale of 43, so it's not totally dead.

Since this must have to do with fuel delivery, I was researching the topic, and found that the injectors furthest downstream from the inlet lean out before the ones closest. #1 cylinder is furthest down the line and showed the most damage, #2 showed some damage, but not as bad as #1... #3 and #4 were running rich. I was getting ok gas mileage (18-20). I own, and was planning on installing a "Stevetek" fuel system w/Adjustable Fuel Pressure Regulator, (see Stevetek.com) and rewire my fuel pump w/ 10gauge. I'd take off the stock fuel rail fittings and weld -6 AN fittings on either side. I did'nt think I'd need it only running 14 lbs. w/out all the fancy ported pieces on the car. Maybe this was a catastrophic misjudgement...

Also, the 1g MAS was peaking at 2200 Hz, and would stay there from 4000 rpm to redline. This seems strange as well. I'm going w/ a 2g MAS w/Dejontool intake tube and all the other mods so it flows better, and gets a cooler intake charge, as well as some hood scoops and louvers to move more air through the engine compartment. I'll also follow your advise (GTM) and put an EGT gauge on the #1 exhaust runner. It is currently running a Fluidyne Aluminum Radiator, but I have not removed the AC yet, will do that w/ FMIC install.

If anyone else has some real experience w/ this I'd love to get your input. This is just theory for me right now, and it's very expensive to have your theory proven wrong in this manner.


Thanks

 

[GTM]

Originally posted by RallyGSX
Thanks for the input, I may have a theory that ties it together.

As far as Detonation, maybe it was detonating just on #1 and #2 and the knock sensor did'nt pick it up for some reason...

I'll also follow your advise (GTM) and put an EGT gauge on the #1 exhaust runner. It is currently running a Fluidyne Aluminum Radiator, but I have not removed the AC yet, will do that w/ FMIC install. and it's very expensive to have your theory proven wrong in this manner.

Yes, I have read the fuel pressure and rail concerns from others. I've not tested this but would like to toss out that the regulator if I'm not mistaken is closest to 1# which would seem to me that would be the highest pressure point if you study fluid dynamics. Now if it's a question of the rail being too small diameter and can't deliver the voluume then you might have a problem across the whole spectrum. It's a math problem figuring max RPM, 660cc (x4 /2) pump delivery (gph) and pressure.


Of course I considered the detonation idea but ruled it out because of the large injectors and the rich running condition which I maintain exists at that altitude. Give me an argument(s) why this is not true...

You could actually put a EGT sensor in both #1 and another after the turbo with a switch where you could monitor either place. I've always used marine grade Pyrometers with 4 1/2" gauge. With these you can watch the gauge move as you power into a wave in a displacement boat or run down the back side. You might find decent units at reasonable prices in a large truck stop for they monitor exhaust temps religeously. You don't have the lag nor the narrow spectrum that water offeres so you get instant readings as conditions change. Best is to have a tell-tale / settable warning alarm so should something start to misbehave it will tell you to back out of it. You can buy a wide variety of probes so they don't cause any restrictions if that's a concern, just don't blind it.

The bottom line is get some more instruments that will help you monitor engine conditions and that should include oil temp as well. They make external sensors which use a spring loaded attachment or a hose clamp to go a round say an oil filter. Home refigerator, freezer, air conditioning hermetic motors have them to prevent motor burnout.

Cheers,
GTM

 

[RallyGSX]

From What I've Just Learned, the pressure at the fuel pressure regulator, and the #1 injector can be lower than at the fuel inlet, because the fuel inlet, and the stock fuel filter are restrictions in the fuel delivery system. Also, the fuel pump does not have a large enough gauge wire to prevent voltage drop from the battery all the way back to the fuel pump, I've heard it can dip under 10 V at times. So if the the problem is fuel supply volume, this theory has it (again, taken from Stevetek.com, check out the diagram at www.stevetek.com/R-FuelSys.html ), #1 injector is going to lose out, and #1 will run lean, #2 a little less lean, and so forth. If fuel supply volume is not a problem, then pressures at each injector will be the same, because gasoline can not compress. This is the basis for thinking the problem could be selective fuel starvation, #1 and #2 running too lean, #3 and #4 running correctly.
Also, can you have lean burn without any Detonation?

Thanks Again, Dave

 

[GTM]

Originally posted by RallyGSX

...
This is the basis for thinking the problem could be selective fuel starvation, #1 and #2 running too lean, #3 and #4 running correctly.
Also, can you have lean burn without any Detonation?

Thanks Again, Dave

Yegads and little fishies. From the article I quote.

"With the help of a local performance shop with a liquid flow bench, I was able to run some flow tests on the stock fuel delivery system. It was found that from the fuel pump outlet to the fuel rail inlet fitting, @ 60psi, a flow of 1.9 liters per minute could be measured. "


Somethins putrid in Peru. Maybe I did my math wrong, but that's in round numbers about 57 GALLONS in 1 hour. If you were driving @ 60 mph you would have consumed 57 GALLONS of fuel.

If he's trying to sell you some $500 package based on those numbers I've got a bumper magnet that will allow you to attach to a 18 wheeler that will improve your gas milage to infinity.

Rewire your pump so you have no voltage drop, that is a known problem.


Cheers,
GTM

 

[RallyGSX]

Well, 1.9L=64.4oz x 60min = 3864.4oz per hr / 128oz/gal = 30.19gal/hr

At WOT, this is not too far off from what a performance car can suck down...

Further, stock injectors are 450cc/min = .45L/min x 4 injectors = 1.8L/min

From "what I've been told" stock injectors max out at about 300 WHP... IF this is true, a 300 WHP car is in danger of using up the available fuel volume. At what percentage of fuel consumption to fuel flow available does the fuel pressure decrease? In other words, if you are using 1.7 of the 1.9L flow available, can the system still maintain pressure? If the Voltage to the Fuel pump decreases to, say 10V, how much does the 1.9L/min figure decrease?

There are a lot of question marks above that I don't have answers to, The only other specs stevetek gives is that his system flows 10L/min (stock pump).
You can buy all these parts listed and rewire the pump for under $200, good insurance, or a waste of $$$?

What other explanations would account for "the meltdown"?

Any big turbo drag race guys out there have some real world experience you'd like to share?

 

[GTM]

Originally posted by RallyGSX
Well, 1.9L=64.4oz x 60min = 3864.4oz per hr / 128oz/gal = 30.19gal/hr

At WOT, this is not too far off from what a performance car can suck down...
...
If the Voltage to the Fuel pump decreases to, say 10V, how much does the 1.9L/min figure decrease?

There are a lot of question marks above that I don't have answers to, The only other specs stevetek gives is that his system flows 10L/min (stock pump).
You can buy all these parts listed and rewire the pump for under $200, good insurance, or a waste of $$$?

What other explanations would account for "the meltdown"? Any big turbo drag race guys out there have some real world experience you'd like to share?

Thanks for correcting my math. Still that's a huge number. I don't think F-1 or giant V8 stock cars do that badly. ?? I as mentioned there is a known problem with voltage drop to the pump but I see no reason for it to cost $200 for #8 gauge wire and a decent relay.

Then his 10/L /min fuel pump is cranking out 600L / hr That's again back to the 30 gallons / hour. Are we taling a 1/2 hp motor pulling 35+ amps continuous? Where do you get that... Alt. of course which is pretty iffy when using the stock 70Amp.

I am somewhat playing the devils advocater but I don't like fuzzy math, gross over generalizations or someone who has an ax to grind.

All this is not sounding very practical as a work commuter or a ralley car.

Meltdown as mentioned could have been a number of things. Too hot a plug, too wide a gap, poor water circulation, poor oil cooling to underside of pistons. Overheat, bad t'stat, clogged radiator, low water, loss of fuel pressure, dirty injectors. Malfunction knock sensor, ign timing advanced, valve timing. Did I miss anything??

Are we back where we started?

Cheers,
GTM

 

[RallyGSX]

Alright, I searched and found answers to the fuel delivery questions at conleyracing.com. They tune Regal GNXs , (3.8L Turbo v6)

It takes .6 lb/hr gas to make 1 hp on a turbo car...
Fuel weighs 6lb/gal, Therefore:

Required fuel = HP x .6 lb/hr , 300HP x .6 lb/hr = 180 lb/hr

Capacity (GPH) = 180 lb per hr / 6 lb per gal = 30 Gallons per Hour

So, you can see this totally confirms my hypothesis that a 300 HP car is using the entire fuel supply available by the stock system! Stock system supplies 30.19 gal/hr.

Also, a 2V drop in voltage to the fuel pump reduces it's efficiency by %15, if the stock pump can dip under 10V, from the alternator putting out 13.8 V or so, you can see were screwed unless we rewire the pump. This 300HP car's fuel requirements ARE NOT met by the stock fuel delivery and electrical systems.

As to F1 cars and NASCAR cars not using this much fuel, we're talking about fuel consumption at WOT, higher RPMs, peak HP production. We are not talking about average fuel consumption arount the track...

Also, the $200 I mentioned includes steel braided fuel line, aftermarket EFI filter and all fittings to totally replace the stock fuel delivery lines from pump to rail as well as pump rewire relay and wires... An Adjustable Fuel Pressure Regulator and fittings from the back of the rail to fuel rtn. line can be had for another $200 or so. The stock regulator can not bypass enough fuel to regulate a high pressure aftermarket pump.

The 10L/hr system stevetek.com has on it's site flows 158.9 Gal/hr, enough gas to supply an approx. 1500 HP monster w/gas... overkills better than fuel starvation.

Items to rule out:
Ignition Timing - logger verified
o2 sensor- logger
knock sensor - logger
valve timing
low coolant
overheat- was running 3-5 deg centigrade too hot for some reason, though...
clogged rad, bad thermostat - new items, even tried 2 thermostats...

Whats everyone else think?

 

[GTM]

Originally posted by RallyGSX
Alright, I searched and found answers to the fuel delivery questions
...

Capacity (GPH) = 180 lb per hr / 6 lb per gal = 30 Gallons per Hour
...
this totally confirms my hypothesis that a 300 HP car is using the entire fuel supply available by the stock system! Stock system supplies 30.19 gal/hr.
...
you can see were screwed unless we rewire the pump. This 300HP car's fuel requirements ARE NOT met by the stock fuel delivery and electrical systems.
...
An Adjustable Fuel Pressure Regulator and fittings from the back of the rail to fuel rtn. line can be had for another $200 or so. The stock regulator can not bypass enough fuel to regulate a high pressure aftermarket pump.

The 10L/hr system stevetek.com has on it's site flows 158.9 Gal/hr, enough gas to supply an approx. 1500 HP monster w/gas... overkills better than fuel starvation.
...
even tried 2 thermostats...

Whats everyone else think?

Thanks for the fuel info and calcs supporting your position. I didn't want us to have wrong info and base solutions/conclusions on faulty data. Good you pointed out what a serious OVERKILL he made choosing a pump that size... He could pump out his swimming pool with that. I'm sure the pump maker was more than willing to take his money. Had someone just taken a couple min. explaining what the calcs showed he needed, something 1/2-1/3 that size without having to have an oversize Alt. to drive the fuelpump. I guess what I'm trying to say is do your OWN homework first before accepting what someone is telling you.

I don't know what's available today, it use to be those Bosch units fitted to VW and Porsche could be adjusted. I had some up to 50psi, that will be a relative number based on input pressures and volume. Maybe some large block Mercedes Benze will have a similar unit. I toss this out so you don't commit to a $200 pressure regulator that may not solve a problem or prove to be satisfactory.
.........

What thermostat ranges have you tried?

Yes, can't we get more participation???

Cheers,
GTM

 

[RallyGSX]

The aforementioned stevetek fuel delivery setup is powered by a STOCK fuel pump!!! This again illustrates how restrictive the stock fuel lines and filter are.

Also, my car was only producing 216 HP and 235 lb torque at the wheel... could this be enough induce fuel starvation?, maybe my fuel filter or pump sock was plugged? I am using Extreme Motorsports (extreme prices) hi-pressure pump. I think it's just a Walbro 255 LPH marked up %50 (judging by the whine). Unless I want to go back to a stock pump, I'll have to use an AFPR so I don't overrun the stock FPR...
You could also use a Denso pump, or a Supra TT pump (both better choices, I now think). Bosch makes a very expensive pump that flows 2x a 255 LPH pump!!!

I was using a stock thermostat. I think it runs 100*C, or 212*F...

 

[GTM]

Originally posted by RallyGSX

...
I was using a stock thermostat. I think it runs 100*C, or 212*F...

Absolutely not!!???? Whoa, hold on, halt!!

Forget everything else that we have discussed as of this writing.

That's the boiling point of water how can you expect this to do anything but go down hill? You must have a cushion especially when pulling more hp, the book may call for a 180-190F t'stat I'd recommend a 170-180 and you check with a good thermometer so you can monitor fan cut in and out as well as monitoring water flow with the cap off. Write the data down so you have it and there is no guess work.

You still have not answered if the 660 injectors are too rich at 9,000 feet????

Replace that THERMOSTAT, then worry about anything else. I grind a small "V" notch in the t'stat so it's in the most uphill position to let the air bubbles out and provide an extra margin of safety.

Cheers,
GTM

 

[mazdamx6pwr.com]

Not to go off topic. But do you have a skid plate? IF so where did you get it?

Adam

 

[RallyGSX]

Oops I was wrong

Stock thermostat opens at 195*F,not 212*F, and yes, I looked around and I can get a lower temp t-stat for my car. V notch also a good idea. Thanks!

My car always ran half gauge w/ new motor, usually ran just below, maybe an indication of preexisting condition?

Also, the 660cc injectors are controlled by a SAFC, fuel trims were calibrated w/ a TMO Datalogger, and WOT was calibrated on a AWD Dyno w/wideband O2 sensor.. A/F ratio was very close.

An "expert" who tunes turbo cars and owns a low 10 sec RX7 looked at the motor and datalogger info. He thought it was running too much timing advance under boost: it averaged 25 degrees, he said the "weakest" injector would cause problems first if fuel delivery was an issue, #1, opposite the fuel inlet had the worst damage, #3 and #4 were undamaged.

Oh, Skidplate: I'm working on building some from aluminum, after this disaster it won't be done very soon, sorry. I could send pics in a couple months... I've heard others on CO Rally page use Carbon Fiber sheets, sound cool, I know nothing about it though.

 

[GTM]

Originally posted by RallyGSX
Oops I was wrong

Stock thermostat opens at 195*F,not 212*F, and yes, I looked around and I can get a lower temp t-stat for my car. V notch also a good idea. Thanks!

Also, the 660cc injectors are controlled by a SAFC,
...
Dyno w/wideband O2 sensor.. A/F ratio was very close.

An "expert" who tunes turbo cars and owns a low 10 sec RX7 looked at the motor and datalogger info. He thought it was running too much timing advance under boost: it averaged 25 degrees, he said the "weakest" injector would cause problems first if fuel delivery was an issue, #1, opposite the fuel inlet had the worst damage, #3 and #4 were undamaged.
...

Re: oops, too bad in a way for we could have laid blame right there. Try for a 170 if you can get it. You can always stick a piece of cardboard in front of the radiator when you need warmer temps. The V notch lets a little water circulate on both sides of the t'stat rather than that pin hole.

As long as you have faith that the 660 injectors are getting the proper control as your altitude changes then we can rule those out as causing a rich running condition or a failure to a temp radical lean.

Of course any injector failure is going to be the weakest link when you are hard on it. Was reading someplace recently that the O2 sensor is just a gross compensator meaning the engine could go lean before it could register and send needed data to correct the condition.

I've seen the timing advance number of 23 offered as most desirable, but if knock sensor is not reliable then find a substitute which you can depend on.

Get the EGT pyrometer on your car, you will find you trust it much more than the water gauge and depending on gauge size and sensor range can give almost instant readings.

Cheers,
GTM

 

[RallyGSX]

Apparently the stock thermostat opens at 195, fans don't come on until 212 deg F, so I'll get a lower temp t-stat, and an adjustable fan thermostat so fans come on a few deg. after thermostat opens.

Other mods I plan on doing so this does not happen again:

Retard timing down to 23 deg advance or less

Hi flow fuel system w/ adjustable FPR and pressure gauge

EGT Gauge on #1 runner

Install Large (24" x 12" x 3") FMIC w/ 2 1/2" piping and 2g MAS w/ Dejontool intake

Evo III Ported exhaust mani. and O2 Sensor housing, 3" Turbo back exh.

Hood scoop and louvers to move more air thru engine compartment

Delete A/C parts

Flow Test and Rebuild Fuel Injectors (send to RC Engineering)

 

[GTM]

Originally posted by RallyGSX

...
Flow Test and Rebuild Fuel Injectors (send to RC Engineering)

Before you do that take a look at what I came across just by accident and see if there is anything in there that might make some sense out of your questions/problems.

Please let us know what you find and how it may fit?

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=47342&highlight=data+logger+computer

Cheers,
GTM

 

[RallyGSX]

I was looking for timing threads, and came across some (hate to say it) more informative postings at this thread, especially tanner261's post: Solution! The fact seems to be that 1gs have too much timing advance when using large injectors and compensating for it w/ a SAFC. Just richening it up to rediculous levels isn't the solution...check it out!:


http://www.dsmtuners.com/forums/showthread.php?threadid=84391&goto=newpost

Thanks,
Dave

 

[GTM]

Originally posted by RallyGSX
(hate to say it) more informative postings at this thread
...
http://www.dsmtuners.com/forums/showthread.php?threadid=84391&goto=newpost

Thanks,
Dave

Not a problem for me, my input was to ensure you had not discounted or overlooked some of the basics. As someone mentioned they keep taking away our ability to diagnose problems when you don't know what the balsted computer is NOT telling you or the engine what it's doing. Then you come across something like "not reported" really is a confidence builder...

If you find out the solution let us know.

Cheers,
GTM

 

[92GSXBaltimore]

sorry for the delay rallygsx. I dont feel like reading all this stuff already posted above so if i repeat sorry. As far as what has caused your "meltdown".....could be a combination of alot of things.
you said that your pistons have been damaged, you could be running lean and therefore melting the pistons. it could have been detonation from a too hot of an air charge(install the fmic you have). As far as the blow by, considering the damage to the pistons and compression readings it is safe to say that your rings are shot. If your

Now to adress your desire to rally race, i would logically perform these in this order
1. engine blueprinted( or at least restored to near original performance and health)
2. safety(harness, rollcage, fire system, engine kill switch....)
3. cooling+suspension
4. weight reduction+engine performance mods
5. transmission

 

[GTM]

Originally posted by 92GSXBaltimore

...
As far as what has caused your "meltdown".....could be a combination of alot of things.
...
Now to adress your desire to rally race, i would logically perform these in this order
1. engine blueprinted( or at least restored to near original performance and health)
...

My apologies also for there have been some PM's which should have been out here for those following the thread.
...........
We were discussing some of the pros and cons of the different piston types currently available. I just happened to ask what clearance he had been running and he reported .0045" total. From my experiences this was just _not_ enough to prevent galling as the pistons are needing more room for expansion. The numbers I have alway used with with my own engines as well as customers which are running forged pistons have been based on .002"-003" _per_ inch of bore. You must not forget to check this at the top and bottom of the stroke with the piston right side up AND upside down when dealing with a used block that has not been bored. Of course you do not use this measurment for the top of the piston nor are you checking above the piston ring swept area. I prefer to use a combination of feeler gages with the base a straight thickness and then a go-no-go which is stepped in .002" incriments. You want a snug fit but not so tight it starts scratching the piston. Though I prefer to use the step gage next to the piston you could use the fixed gage next to the piston and the step against the cylinder wall. You can get some grease type Prussian Blue and smear on the opposite side of the piston to get a print of exactly what the piston looks like when contacting the piston wall. It is best to use a conventional hone rather than a glaze breaking bead hone when taking these critical measurments. Any questions?

.................

Don't know if this is a good place to discuss blueprinting but you summary was to the point.

Cheers,
GTM

 

[RallyGSX]

Thanks for the response 92GsxBaltimore (I grew up in Hartford County).

I will check w/JE tomorrow to clarify the correct clearance for their pistons. The instructions that come with the pistons stipulate a piston to cyl. wall clearance for "sport compacts" w/ 2.5 to 3.625" bore range as .0030 to .0036 as a minimum. The pistons are made of a non-silicon aluminum alloy, so they don't expand as much as a silicon containing piston. Also, JE says "clearances listed are minimum. Some applications such as supercharged, turbo, nitrous, and endurance applications may require additional clearance (.001 to .003"). So .0045 may not be too far off. The machinist said the piston skirt scuffing was a result of the pistons getting too hot? Also, at least one connecting rod was very tight at it's connection to the piston wrist pin. When it is rebuilt, I am going with Ross 8.5:1 .030 over pistons. I believe the engine may be less likely to detonate with the lower compression ratio with minimal loss of transient boost response and power...

Other factors I now know were off, and contributed to the catastrophy...

Timing was too advanced... I'm getting a reprogramed Eprom for my ECU through DSMchips.com that compensates correctly for the 660cc injectors, thus ECU reads correct timing maps

Coolant temps too high... factory fans don't come on until 212* F, rewire fans w/adj. thermostat, lower coolant thermo to 170-180

Stock fuel system inadequate... Rewire pump, Stevetek fuel sys, AFPR. I believe engine was running lean at HP peak.

High Underhood Temps... Hood scoop, louvers, punching holes thru front bumper (six 2 1/2" holes) to allow top of FMIC/radiator to get direct airflow. Removing A/C system.

Intake air temps too high...install FMIC (24 x 12 x 3"), MAFT

Malfunctioning Knock Sensor... Could the knock sensor read a high knock count of 3 and this still happen???

Restricted Exhaust... Will use ported EVO mani, O2 housing, 3" exhaust instead of 2 1/2", ported head...

Any other ideas / input appreciated!!!!

Input on what pistons/compression ratios are best...

Any other Engine Building Procedures beneficial to a high performance turbo motor...

Thanks!!!