I'm opening this thread as an advanced discussion to try and figure out why I'm having spool issues on a stroker with only a medium sized turbo. You can review my mod list to see exactky what's in the motor. Trust me it's not all that much.

At the moment, I see full spool at 4400-4600 RPM depending on weather while runniing a 3rd gear pull from 2500 RPM. The turbo has a tendency to struggle to make boost until it hits 10 psi and then it shoots skyward pretty quickly. While running 1-2-3 shifts, it's not an issue since the motor is already spooling and pulling hard, but it's a bit disappointing from a 3rd gear pull. I wouldn't care if I could run the motor to 8000, but I'm shifting at 7000 due to the rod angle. Here's a laundry list of the things I've tried with the suggestion of my fellow wiseman who have been extremely helpful in their PM's.

- Leaned out the A/F to 14:1 at the onset of boost gradually increasing to 11:1 after 4600 RPM. The extra heat should have increased spool, but did nothing.

- Boost leak tests were performed at up to 26 psi. The system held 26 for 20 seconds before starting to slowly bleed down.

- Reduced fuel volume to the rail by lowering base fuel pressure from 43 to 38 psi. All this did was run me into knock on pump. There was a minimal effect on spool, but it was negligible.

- We reduced timing advance in the midrange to once again generate more heat. This just made the motor feel like a turd instead of providing any positive result. The timing were changed back to stock 2G that ramp to a max of 12 degrees of advance under the 4 highest load/airflow maps.

- Compression on all four cylinders with the Comp 200's (straight up) is 175-175-175-180 across the board. The motor does not smoke, eat coolant or behave erratically except for minor idle issues resulting from pulling the lower honeycomb on the 2G MAF.

- A vortex breaker honeycomb was installed between the intake and compressor inlet. This actually hurt spool and made the MAF erratic in the higher RPM's and negatively affected performance across the board.

- There is one small exhaust leak at the wastegate to dump tube connection that can be smelled, but not heard, when the motor is cold. As soon as it warms, the leak disappears and there are no other leaks at the turbine to O2 or manifold to head. The manifold to head gasket was also replaced at the time of installation with an EVO metal gasket.

- Cam timing is correct and I verified that the motor was dead on the timing marks with the motor at TDC. I was hoping it was off by a tooth (retarded but it wasn't)

There are a few things which I think it may be related to and I'll share them here:

- My cams need to be degreed with adjustable gears. I'd likely get the car on a dyno and advance the intake cam a few degrees while retarding the exhaust cam one degree.

- I'm feeding a turbo that has a 3" inlet with a 2.75" dejon intake pipe. While the system has an adapter coupler on it, I'm not sure if this is making a difference or not.

- I'm running a stock intake on a stock head. I'm not sure if these are creating significant flow restrictions but I have plans to at least change the intake manifold. While I know it will increase VE and overall power, I don't think it would do much for my spool condition. I also run a large sidemount (Dejon) and I wouldn't think that this is holding me back as a flow restriction point.

For reference, the motor is tuned with an EPROM ECU only. I have custom A/F maps that are flat across the board at 11:1 and 12 degrees of max timing advance since the leaner maps did nothing for me. Since I have the ability to see knock, I don't use a logger or bother with EGT anymore. I can only guess at the airflow numbers, but at 30 psi and 6000 RPM, I overran the MAF badly hence the removal of the lower honeycomb. Since the 2100 won't hold that much boost, I run 25 on a daily basis.

I'd love to hear some suggestions, but at this point I'm thinking that I need to at least pick up one adjustable cam gear and dial in the cam timing on the intake with a few degrees of advance. Other than the spool issue, the motor runs exceptionally well and I'm pleased with it. I'd just love to bring the power online sooner. Interestingly enough, even the 16G performed in a similar way by spooling 24 psi around 3600-3800 RPM. It's a bit disappointing if you ask me.

Helpful suggestions are encouraged and thanks for reading my novel,

Andy

I had a similar problem when I first installed my 60-1 on the 2.0. I wasnt seeing full boost(25psi) untill 4800-5000 rpm. After several day of trying to tune for quicker spool, I ran across some useful information.

According to pte, I am supposed to run a -4an feed line unrestricted from the oil filter housing. According to garrett, the turbo was getting too much pressure at the oil feed which was hindering spool times. They stated that the garrett journal bearing chra should see a maximum of of 55-60psi. After some testing, my feed pressure was found to be at 90+psi at wot. I decided to restrict the oil feed to .078" and it made a night and day difference in spool times. My inlet pressure is now 60-65psi at wot and I see 25psi around 4300 and spool recovery is 100% better than before.

That's some very interesting info Keith. I have noticed that at WOT, I'm pegging over 100 psi on the oil pressure gauge and that I'm seeing a teeny bit of blue smoke under full boost. The turbo has zero shaft play so based on what you're telling me, I may be getting too much pressure through the -4 feed, which is unrestricted and pushing a bit past the seals.

Good stuff man! I'll definitely add a restrictor and see what that does. I wonder if my thicker oil (15W-50) isn't helping matters either. Off the cuff, do you have any good sources for a restrictor? I'll do some searches in the meantime, but I trust what you're telling me implicitly.

Thanks much!

andymoraitis said:

That's some very interesting info Keith. I have noticed that at WOT, I'm pegging over 100 psi on the oil pressure gauge and that I'm seeing a teeny bit of blue smoke under full boost. The turbo has zero shaft play so based on what you're telling me, I may be getting too much pressure through the -4 feed, which is unrestricted and pushing a bit past the seals.

Good stuff man! I'll definitely add a restrictor and see what that does. I wonder if my thicker oil (15W-50) isn't helping matters either. Off the cuff, do you have any good sources for a restrictor?

Thanks much!

Click to expand...

I have seen some vendors offer restricted fittings but being a cheap dsm owner, I opted to make my own. I also have a lathe in my garage so making it was a breeze. I just machined the flare off of the inlet fitting and used a nitrous jet as an insert to restrict oil feed. This also made it easier while testing because I could just unscrew the line and swap the jet to a different size.

When looking for a restricted fitting, be careful because most on the market are designed for ball bearing turbos and the orfice will be smaller than what is needed on a journal bearing turbo. If you cant find anything, let me know. I can always pick up a standard fitting locally and machine it for a nitrous jet and send it to you.

This is Paul's old turbo and apparently, he already came up with a restrictor for it:

http://www.dsmtuners.com/forums/showthread.php?t=171317

I need to see if it's still installed, but since we swapped parts directly from his motor to mine, I don't see why it wouldn't be on there.

That is exactly how I made mine. Unfortunately, his write up wasnt on here when I did mine so I didnt have a reference to go by. I guess we just think the same way when it comes to issues like this.

I'm a bit disappointed because I want to find something that's glaringly wrong and I can't seem to. I'm reaching here, but I'm wondering if I shouldn't switch to a thinner oil to see if slightly lower pressure will help. 15W-50 is pretty thick stuff and may be having some type of effect. On the other hand, I still want to offer the motor the best protection I can.

On a related note, these T04B's were supposed to have problems with the seal on the compressor housing. Apparently, Paul took care of that and RTV'd it so we can cross that off the list as well.

Back to the drawing board...

I just talked to Paul about this and he told me that he didn't use a restrictor on this turbo. Maybe we should give it a shot.

Yeah his restrictor was on a his old V-trim I believe, and I thought he told me thats what killed it.

Andy, I'd cross the oil weight off the list too, I ran the same Mobil 1 15w50 full syn in mine and I saw 25psi by 3600-3800.

I installed a set of FP2x's a couple months ago and they were off a couple degrees when installed straight up. I think it's stupid that the retailers say you can install them straight up, it's usually not true. That might be part of your problem.

Dan: I'm going to give Bullseye a call today and see what they say about the restrictor before Keith takes the time to make one for me. I know the V-trim's were surge prone and I would think that this was the reason for Paul's turbo dying moreoso than oiling issues, unless it was starved. Nevertheless, Garrett recommends it and this turbo does run a Garrett center section.

Luke: I agree about the cams. I'm going to invest in a set of Fidanza adjustables as soon as I can to dial the cams in. The strange thing is that Dan also runs the 200's straight up and has much better spool than I do. The again, He runs a different center section than I do (Turbonetics). What has me believing that oil pressure to the inlet is too high is the light tinge of blue I get at WOT despite the absence of shaft play.

As an FYI, here's some information from Garrett on the use of oil restrictors:

Does my turbo require an oil restrictor?

Oil requirements depend on the turbo's bearing system type. Garrett has two types of bearing systems; traditional journal bearing; and ball bearing. The journal bearing system in a turbo functions very similarly to the rod or crank bearings in an engine. These bearings require enough oil pressure to keep the components separated by a hydrodynamic film. If the oil pressure is too low, the metal components will come in contact causing premature wear and ultimately failure. If the oil pressure is too high, leakage may occur from the turbocharger seals. With that as background, an oil restrictor is generally not needed for a journal-bearing turbocharger except for those applications with oil-pressure-induced seal leakage. Remember to address all other potential causes of leakage first (e.g., inadequate/improper oil drain out of the turbocharger, excessive crankcase pressure, turbocharger past its useful service life, etc.) and use a restrictor as a last resort. Garrett distributors can tell you the recommended range of acceptable oil pressures for your particular turbo. Restrictor size will always depend on how much oil pressure your engine is generating-there is no single restrictor size suited for all engines.

Ball-bearing turbochargers can benefit from the addition of an oil restrictor, as most engines deliver more pressure than a ball bearing turbo requires. The benefit is seen in improved boost response due to less windage of oil in the bearing. In addition, lower oil flow further reduces the risk of oil leakage compared to journal-bearing turbochargers. Oil pressure entering a ball-bearing turbocharger needs to be between 40 psi and 45 psi at the maximum engine operating speed. For many common passenger vehicle engines, this generally translates into a restrictor with a minimum of 0.040" diameter orifice upstream of the oil inlet on the turbocharger center section. Again, it is imperative that the restrictor be sized according to the oil pressure characteristics of the engine to which the turbo is attached. Always verify that the appropriate oil pressure is reaching the turbo. The use of an oil restrictor can (but not always) help ensure that you have the proper oil flow/pressure entering the turbocharger, as well as extract the maximum performance.

I talked to Jon at SBR and he recommended it based on my oil pressure readings, but I'm going to talk to Garrett anyway.

Im not talking from experience on this subject Andy as you know, but after reading all the posts and your symptoms, the most sencible problem in my mind is your oil pressure being too high. The blue smoke coming out confirms it, the pressure is so much that it is pushing the oil past the turbo seals (but you probably already knew that). If the oil pressure is too high it seems like it would put excesive force on the turbo and impeading spool time. I would say go with what Keith suggested, and put a restrictor on there. When I saw you posted in this thread I was thinking to myself,"Hey Andy has a similar problem to this." And what do you know, you made the thread

Dustin

I had a chance to talk with a technician at Garrett this morning and he confirmed that if oil pressure readings are over 100 psi on an aftermarket gauge that the turbo's definitely getting too much oil pressure with a -4 feed line. This explains the blue tinge at WOT and also the slowness in spool. He also mentioned that optimal oil pressure for the turbo would be 55-60 psi on a 360 journal bearing setup and that's what we'd normally see on one of our motors with the balance shafts in place. As a result of the excess oil pressure and the drain's inability to funnel off said excess, the turbo struggles or labors until it has enough energy build up to spool quickly. This is coincides with the way my turbo labors to build 10 psi after which it shoots up pretty quickly.

As an aside, I asked him about using a restrictor on a stock motor setup (with balance shafts) and he said that it can certainly deprive the bearings of adequate oil supply and fry the turbo within a short period of time. Maybe that's why Paul's V-trim bought the farm.

I'm going to move forward with this and Keith has kindly volunteered to set me up with a .078 restrictor. I'll post the results after swapping the restrictor in place.

Good to see that you are one step closer to figuring out your slow spool problems Andy, perhaps this was the problem with the slow spooling 16G as well.

Dustin

I think it may have been an issue since the 2.3 spooled the 16G more slowly on the Comp 200's than the 2.0 did. It wasn't much later, but it's almost as if the extra displacement had no effect because the oil pressure was too high. I suppose that this is one of those cases where it's great to have high oil pressure in the motor, but not going to the turbo. We'll find out in the next week or so.

Truthfully, I think I'll crap myself if this thing spools 25 psi by 3800-4000, but I'm not going to get my hopes up until I try it and see.

Interesting thread, Andy. I hope this restrictor works for you.

I ran my v-trim with that restrictor from the start and it always spooled quickly, so I have nothing to compare it to to see if it helped spool. The v-trim blew due to surge. The surge slowly causes enough shaft play to where the compressor wheel was skimming the compressor cover cause the siren whine and slow spool and boost response. Upon disassembly and inspection, the shaft was not burned blue, so we rules out a lack of oil.

Ohh, and I too would also rule out the oil weight. I've typically always ran a full synthetic 20w50 on my turbos and they loved it.

Also, switching to a post-turbo GM MAS set-up could help with spool-up. Matt (blackGSX2g) saw relatively large gains in terms of spool time from switching from his 2G MAS to the MAFT set-up.

What prompted me to make that restrictor was over-oiling on my old 14b. There was too much oil pressure going to it and it started blowing past the CHRA's piston ring pretty quick. I was afraid it would do it to my v-trim too, so I made the restrictor. I'm not sure if I ever really did need it though. The Garrett turbo's can handle more oil pressure than most MHI turbos, and being that I still have my b-shafts, I decided not to run the restrictor until I actually tested the oil pressure in my feed line. And I never did get around to testing for that.

92awddsm said:

I decided to restrict the oil feed to .078" and it made a night and day difference in spool times. My inlet pressure is now 60-65psi at wot and I see 25psi around 4300 and spool recovery is 100% better than before.

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Man, I am completely blown away by that. I couldn't imagine it would make that much difference. I'm looking forward to testing mine this coming spring to see if I can benefit from running my restrictor.

Thanks for jumping in Paul. I may add a GM MAF in the future, but I want to see just how far I can take the stock MAF especially since I have the lower honeycomb out. As far as the oiling capacity, Greg from Garrett mentioned that while the excess pressure wouldn't harm the turbo that it was providing less than optimal conditions for spool and spool recovery between shifts. I too find Keith's results amazing.

We'll see how it works out. I think between this and the cams, I should be able to get the turbo to spool where it should be hitting.

When I was doing research, some of the answers became pretty obvious after pointed out.

The main reason high oil presuure reduces spool time is because a brass journal bearing is actually a floating bearing. With the proper oil pressure, the bearing is supposed to spin in the center cartige while the shaft spins inside the bearing. This in turn reduces the rpm of the shaft in relation to the bearing. If oil pressure is to high, the excess pressure forces the bearing into the housing and causes it to bind while the shaft is still spinning. This effectively increases shaft rpm in relation to the bearing. This creates more drag, which in turn, lowers spool time and maximum spool rpm. For this same reason, maximum achieveable boost pressure is also reduced.

I hope that makes sense.

It sounds like you guys are coming to a conclusion before I had the chance to jump in at all. I have to say that the higher oil pressure would have passed me up because much of my experience with non-balance shaft/ high oil pressure motors is on ball bearing turbos. Great job guys.

Other considerations: I love the MAFTs or map setups. The increased spool and overall flow gain over a more restrictive sensor is awesome. I think this will really help when you are at that point.
The other thing that I wanted to mention is the 7000 rpm limit you have set for your self. I just wanted to add that strokers will put up with more rpm then that with out problems. I think alot of it depends on the use. If your car were a rally car or something of that matter, I would keep it lower like you do. Otherwise, I drive mine less as a daily and more as a weekend or track car, but I see in 9600 rpm on a very regular basis. I know that piston speed and everything else comes into play with this. But again we are not doing this the entire time its going down the road. I hope I am not starting a in can/ in can't discussion. I am just saying, the idea of you taking yours out to 7800 or so is not going to kill it any time soon.

The only other input I could give with the info available is: Most pore spool issues I have seen have been boost leak or wastegate related. PTE turbo leak like crazy from the compressor cover in example. I have a good friend with a 2.3 in a 99GSX and he wasnt seeing full boost until ~5200 rpm. Sealing the cover alone brought it down to about 4300 rpm. The other thing I have seen a few times was the wastegate fire ring/ valve seat pitted badly. 5bucks or so for a new one and spool increased greatly again. (I dont remember the exact specs on this situation.)

Personally I am able to spool 45psi on a 94mm 42r by ~4600 rpm in third. (hard to say in the lower gears.) I dont know the cams you have very well, but as input on that topic, I am running HKS 272. Stock cam gears.

I am very interested in the restictor idea, and would love to hear what happens. Keep us posted.

I hope I was able to help,

Jake H

92awddsm said:

I hope that makes sense.

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It certainly does Keith, but I think you meant that high oil pressure increases (not decreases) spool time. Are you hanging around me too much and getting things backwards? Sorry, I seem to have that effect on people.

topstreet said:

It sounds like you guys are coming to a conclusion before I had the chance to jump in at all.

Click to expand...

Hell no Jake. The boys and I were just keeping things warm for you. Thanks very much for jumping in and lending a hand. I have the rev limiter currently set to 7800 and my cams (which are similar to 272's) peter out at close to 7400 so I don't think it would be a huge issue to run the motor to 7400-7500, but I didn't want to create any issues due to piston speed and rod angle. Some shops have said never to go above 7000 and people like yourself and Kevin Jewer have gone higher. Believe me, I'd love to try another 400 RPM of usable power.

On to some of the you were mentioning. I agree that the MAFT will be the way to go and I may eventually add one. Regarding the cover leaks, the B-cover 50 trims were notorious for this, but I remember Paul telling me that he RTV'd the cover so we can cancel that out. Other than that, I think we'll find something between the high oil pressure and the cams. If the cams aren't truly straight up and are a couple degrees retarded out of the box that would certainly explain a lot.

I really appreciate that you took the time to share some firsthand knowledge. Maybe we can talk optimal stroker timing sometime?

I'll keep everyone updated when Keith sends me the restrictor and I suppose we can work from there. I also want to take a moment to thank everyone who's contributing to this thread with their expertise. You guys are highly intelligent and I learn just from listening to you.

Have you ported your oil filter housing?

92awddsm said:

When I was doing research, some of the answers became pretty obvious after pointed out.

The main reason high oil presuure reduces spool time is because a brass journal bearing is actually a floating bearing. With the proper oil pressure, the bearing is supposed to spin in the center cartige while the shaft spins inside the bearing. This in turn reduces the rpm of the shaft in relation to the bearing. If oil pressure is to high, the excess pressure forces the bearing into the housing and causes it to bind while the shaft is still spinning. This effectively increases shaft rpm in relation to the bearing. This creates more drag, which in turn, lowers spool time and maximum spool rpm. For this same reason, maximum achieveable boost pressure is also reduced.

I hope that makes sense.

Click to expand...

Great post, Keith. That makes perfect sense.

andymoraitis said:

Regarding the cover leaks, the B-cover 50 trims were notorious for this, but I remember Paul telling me that he RTV'd the cover so we can cancel that out.

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Andy, I'm like 99.7% sure I RTV'd it, but not 100% sure. If I were you, I'd double check it just to be on the safe side. But then again, if it were leaking, you would have caught it on the boost leak test.

andymoraitis said:

It certainly does Keith, but I think you meant that high oil pressure increases (not decreases) spool time.

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Andy from what I have read I think Keith has it right that it decreases spool time, if the oil pressure is too low the bearing doesnt have enough oil to float, and if it is too high the pressure pushes down on the bearing, creating friction and there for slowing spool. When the oil pressure is between 55-60psi it doesnt have too much pressure pushing the journal bearing, and creating friction with the shaft, and its not too low and starving the bearing of oil to "float" on, and killing the turbo quickly. Im sure Keith will be on soon to clearify. Just had to chime in my seemingly endless .02

Dustin

andymoraitis said:

I'd love to try another 400 RPM of usable power.

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A quick point that I want to bring up about this is torque band. Now you may come up in power and start to see a mild decline in the power at aroung 7400... But where is your power in the next gear? This is very important in a race. The reason I take mine to 9600 rpm is not because it is continuing to push power at this point, but more because when I shift (lower rpm) it drops lower in rpm (toruqe band) then I want.

For example: If I take my car to 8800ish (~600rpm past peak power) and then shift. I end up around 6400ish... This brings my torque and HP down around 120-150. If I take the rpm past the peak power to about 9200ish, I will loose about 40-50 torque/HP. At this point, coming into the next gear starts me off with only 50ish horse shy of peak.

Long story short: I can stay within about 50-60 lb/ft of torque, and 100 horse power before or after peak. Instead of loosing about 30ish past peak and 150ish going into the next gear.

I hope I am making sense or explaining myself well enough.

If this isn't clear enough or if there are aspects you would like explained better, just let me know.

Jake H

Yeah Jake that makes sence to me, very nicely stated. I doubt I will put my future FFWD stroker past 7400rpm though. We will see

Dustin