reducing spool times

[1gDSM4g63]

Equal length manifold.

Yup, ported, honed internal with gasket matching runners.

Bagging the turbine side of the turbo.

4" =< larger turbo intake.

properly matched intercooler and short route piping.

Larger the better CFM rating intercooler.

Small/stock cams.

I don't know about going with small degree cams. It would decrease the lag, but it defeats the whole purpose of going to a big turbo. The high degree cams that matches with the spool will unleash the power of what a big turbo is capable of. If you don't know what I'm talking about you're definitely missing out. It is like you're riding in a rocket once it kicking in, it's the BEST high you will ever have.

 

[dwdsm]

Yup, ported, honed internal with gasket matching runners.



4" =< larger turbo intake.



Larger the better CFM rating intercooler.



I don't know about going with small degree cams. It would decrease the lag, but it defeats the whole purpose of going to a big turbo. The high degree cams that matches with the spool will unleash the power of what a big turbo is capable of. If you don't know what I'm talking about you're definitely missing out. It is like you're riding in a rocket once it kicking in, it's the BEST high you will ever have.

I rock 272's so I know what your talking about. However there was a guy around here running 280's on a 16G... Now what the hell is that going to do.
So how about properly matched cams
With intercoolers bigger doesn't always mean better it's all about efficiency and keeping your intake velocity up. lag comes from filling the "void" of a giant intercooler, endtanks, and long ass piping. Mine for example is way over kill. I could of went smaller and saw slightly quicker spool therefore more midrange. But I was stupid and went for the biggest one I could get my hands on..BTW I have the kenitic fmic.

 

[1gDSM4g63]

Well some don't sl-lit and thing big is better, good thing he didn't know 288 cams existed.

As for big intercooler, it shouldn't make that big of a difference if you go bigger. If you have a big turbo and a small intercooler rated for less air flow then again a big turbo is useless. It'd be impossible to come even close to what the turbo's air flow is capable of without knocking. We all know that running 15 psi. vs. 30 psi. on big turbo generates far less then half the hp.

 

[gixxerdrew]

run nice and lean in spoolup, in the real world you'll do better with a manifold like the FP cast mani than with any long runner. I think you need the really massive headers to get to less lag than you get from the shorties. It's actually very substantial.

On DSMLink I used to get this by using the maf adjusters. With AEM just lean out that part on the map. It will also help your gas mileage. Below 3 psi boost I go as lean as possible without studdering. Everyone told me a big IC (mine is really big) and big piping would be laggy. I have 3.5" piping, a Q45 TB and a venom intake mani. I noticed no lag at all from the change. In fact I think it spooled faster.

You can also effect lag a lot with head porting, a few hundred rpms easily. The problem is trying to keep that in line with topend power sacrafices.

 

[dsm-onster]

Amen! Heat spools a turbo. Lean is hot. Turbine work = Massflow X Specific heat X (Temp in - Temp out). The more work the turbine can extract from the gases, the faster it can spool the compressor.

This is one reason why no exhaust works so well to spool a turbo. And helps peak flow as well because the turbine can get more work out of the exhaust gases without having to use so much massflow to do it, which is the other variable. The massflow can be wastegated, engine VE goes up and your overall flow goes up. Simply no exhaust or at least a large exhaust puts cold air closer to the "temp out". No one even mentioned exhaust upgrades .

 

[1gDSM4g63]

Everyone told me a big IC (mine is really big) and big piping would be laggy. I have 3.5" piping, a Q45 TB and a venom intake mani. I noticed no lag at all from the change. In fact I think it spooled faster.

You can also effect lag a lot with head porting, a few hundred rpms easily. The problem is trying to keep that in line with topend power sacrafices.

That's good to know it doesn't cause lag, I can relieve myself of doubting what I have done going with the Q45 TB, race SMIM, ported the block and head.

 

[xxsupralvrxx]

ummm not to sound like a noob but what is "SMIM"?
what about exhaust cut outs?

 

[T9S1i]

smim = Sheet metal intake manifold
Like a magnus, jmf, etc. etc.

 

[jrohner]

Leaner doesn't always put more heat in the exhaust. My old yamaha atv was really cold-blooded and needed the choke (enrichment actually) on for a few minutes before it would run decent. With the choke on, more than a foot of the the exhaust glowed so red you'd think you could see through it. No it did not glow like that once I turned the choke off.

How would a huge intercooler ever HELP spool? When I finally ditched the side-mount for a huge front-mount, my spool rpm went up about 300 rpms.

When I then went from stock 2g cams to BC272's (using stock cam gears, no degreeing), my spool did not change one bit. Exactly the same spool, and increased power everywhere. The cams did not hurt the amazing surge of torque, or start it at a higher rpm, it just carries it up higher in the rpms.

As for running lean, I run extra lean to try gain some MPG's and my car has NO POWER until the boost hits and I'm positive it's at a HIGHER rpm than when running a stoich mixture.

Also, even if running low timing helps spool (which I'm positive it does), the torque is hurt so much with lower timing I don't see how it could be worth it. Your turbo may have spooled at a lower rpm, but you would've gotten to a higher rpm faster anyways with more timing. You got a lower rpm spool, but the guy next to you running more timing is already ahead of you by then!

 

[Car Cannibal]

Free up as much backpressure in the inlet and exhaust as possible. This means running mafless with 4" piping, low pressure drop FMIC's with 2.5" tubing, bigger TB's flow more and anyone who's done the mod will notice the creeping of boost ( freed up backpressure in the inlet system ) and the other mods people have said.

1992awdlasers post is great for manual cars, not so for automatics. Automatics need torque to get the converter up, retarding the timing makes less torque so for auto's you need high timing and leaner AF/R to gain torque and get the converter up, a transbrake would help even more to achieve actual stall speed.

There is a twin scroll housing actuator out there that will close off the inside port to the exhaust wheel and as you come up on boost it opens that port for mid and top end flow. That's something that can help every big turbo car.

 

[RipperXX]

gixxerdrew makes some since there. I have always just thought when I finished mysetup and got around to tuning it I would just max the timing in the off boost and low boost. But I supose leaning it out makes since too. Maybe a mild combo of the two? Both make more power without boost so either way it would be more responsive than left at factory settings.

Sounds to me like some experimenting is going to be needed to see which tuning method gives the best results of X setup. I personally have a small turbo though so lag isn't really an issue for me. None the less I still plan on putting a turbo blanket over the turbine side and some exhaust wrap on the down pipe.

I would put it on the manifold and O2 houseing but.... The Manifold is a Evo III manifold, and besides being a bi*** to wrap (have seen good jobs of it though) I am not sure if this will seriously reduce the life span of the manifold. Same for the o2 housing. It's a tubular piece, nice welds and thick flanges but still not sure wraping it would be a good thing for reliability. So I am thinking just a "turbo blanket" and some wrap on the down pipe with high temp sealent.

Also I see no reason polishing the inside of the OEM intake manifold and gasket matching it would hurt low end, if anything it should improve VE and spool faster.

 

[delta448]

Amen! Heat spools a turbo. Lean is hot. Turbine work = Massflow X Specific heat X (Temp in - Temp out). The more work the turbine can extract from the gases, the faster it can spool the compressor.

This is one reason why no exhaust works so well to spool a turbo. And helps peak flow as well because the turbine can get more work out of the exhaust gases without having to use so much massflow to do it, which is the other variable. The massflow can be wastegated, engine VE goes up and your overall flow goes up. Simply no exhaust or at least a large exhaust puts cold air closer to the "temp out". No one even mentioned exhaust upgrades .

You missed a post.

Decreasing airflow restrictions at the compressor inlet (think MAFT, true CAI setup).
High-temp insulating exhaust wrap on the manifold.
External wastegate with an EBC.
A true divided turbine housing with the appropriate true divided manifold.
Removing exhaust restriction after the turbine; think no-cat, large dia. piping, DP cutout, etc.
Good results from a boost leak test.
Retarding the exhaust cam a couple of degrees.

 

[dwdsm]

Now as far as exhaust is concerned the Ideal set up is to have a straight pipe with no mufflers or cats or any thing to disrupt the air flow. Now, I was always told that an exhaust should also match your set-up. Example a 16G flowing 38lbs. per min should run a 2.5" exhaust to keep velocity up (hot air moves faster). Pretty much the bigger the turbo the larger pipe is required for efficiency. I have a 50trim so I went 2.5 to the flex and 3 behind that considering when the exhaust starts to slow down it will have more space to fill and not be turbulent. But some believe you should make it as big as possible to not allow any back pressure. Can you go to big on a small turbo? Discuss.

 

[xxsupralvrxx]

as the gases cool dont they contract an get denser(sp?)?

 

[RipperXX]

Yes just like how "air" is dencer the cooler it is. Exhaust is the same way, hot = thin, which is easier to move. Colder = dencer, heavier, harder to move.

If you have noticed drag race turbo cars sometimes have side exhaust. with it running from the turbine side of the turbo out the side bumper. This reduces back pressure to almost non-exsistant. Which BTW is optimum for a turbocharger. N/A type stuff doesn't really apply to turbocharged setups. It does however still apply to super chargered cars as the exhaust is the same as N/A and things like scavaging still help. On a turbo car the back pressure that is present from the cyl to the turbo it's self I think more or less prevents much of any scavaging effect, I could however be wrong.


In short, larger is better for max HP. Also the faster the turbo spools the sooner X amount of boost is reached. With that said more power can be made at a lower RPM resulting in more torque as well.

 

[delta448]

^I agree with this post.
To add:

As exhaust cools, it indeed condenses into less volume for the same mass (or less pressure for the same volume) and it's velocity slows down. Also, gases under pressure cool as they expand into a volume of lower pressure. Most of the expansion and cooling takes place as the exhaust passes from the volute past the turbine blades. The more volume the exhaust has available to expand into, the more it cools and the greater the pressure difference becomes across the turbine.

A higher pressure differential across the turbine results in more work being done by the turbine. -Which acts on the compressor and creates the higher compressor rotational speeds necessary to produce positive boost.

As far as a turbocharged car's exhaust is concerned, you can't really go too big or too short. However after you reach a large enough piping size going bigger just takes you further into quickly diminishing returns.

 

[ApexVIII]

What you want to do is retard the timing and add fuel pre-spool.

Retarding timing will make it spool faster. It does this because more of the heat from the power stroke goes into the exhaust manifold. I will try to explain each.

When timing is advanced the spark ignites the air/fuel mixture at a sooner point. This gives the mixture more time to burn in the cylinder. Most of the heat from this will be absorbed by the engine itself. The reason this makes more power is because the mixture has a longer time to burn before the piston reaches tdc. Since it has more time to burn it is going to make the pressure pushing down greater. This is where the exrta power comes from. More pressure downwards when the piston is at tdc. This is also why advancing timing can create knock or pre-ignition.

Retarding the timing makes the mixture start to burn closer to tdc. This will make less power since the mixture has less time to expand before the piston reaches tdc. Retarding will cause some of the mixture to be burning when the piston is moving down and when moving up on the exhaust stroke. Since the mixture burns later the heat has less time to be absorbed by the engine and as a result it will go into the exhaust manifold which will help spool the turbo. The mixture burning during the exhaust stroke also causes the turbo to spool sooner since the mixture is burning with the exhaust valves open. This is how antilag works, it retards timing so the mixture is burning when the exhaust valve is open.

When you add the fuel, the mixture will be burning longer since there is more fuel to burn. This will also cause the mixture to burn when the exhaust valves are open which makes the turbo spool faster. When the spark plug first goes off all the fuel doesn't burn right away. The fire spreads outward away from the spark plug. Since the flame spreads outward it takes time for all the fuel to burn. So, if you add fuel there is more fuel to burn which equals more time it takes to burn all of it. That translates into some of the fuel burning when the exhaust valves are open. This is another way of knowing how adding the fuel help.

so would you say that advanced timing would be good for a race like AutoX or something

and retarded timing maybe for a Drag, or Road race?

 

[dwdsm]

Whoops I knew that cooler was denser.. Just a brain fart there. late night working on the DD Metro.
I want to know what some of you guys do for a living? I get so schooled on here at times. That's a good thing tho.

 

[dwdsm]

so would you say that advanced timing would be good for a race like AutoX or something

and retarded timing maybe for a Drag, or Road race?

I could go with that! Also advanced for longevity (I would think) and possibly street.

 

[dsm-onster]

How would a huge intercooler ever HELP spool? When I finally ditched the side-mount for a huge front-mount, my spool rpm went up about 300 rpms.

When I then went from stock 2g cams to BC272's (using stock cam gears, no degreeing), my spool did not change one bit. Exactly the same spool, and increased power everywhere. The cams did not hurt the amazing surge of torque, or start it at a higher rpm, it just carries it up higher in the rpms.

As for running lean, I run extra lean to try gain some MPG's and my car has NO POWER until the boost hits and I'm positive it's at a HIGHER rpm than when running a stoich mixture.

Also, even if running low timing helps spool (which I'm positive it does), the torque is hurt so much with lower timing I don't see how it could be worth it. Your turbo may have spooled at a lower rpm, but you would've gotten to a higher rpm faster anyways with more timing. You got a lower rpm spool, but the guy next to you running more timing is already ahead of you by then!

Going from a small intercooler to a larger one increased my spool speed. I also gained lb/min flow. More massflow increases work done on the turbine. I don't see how you don't think this is possible. I know filling a larger volume increases lag, but after 1st gear, isn't the larger intercooler filled?

272s made my small 16g and 18g more laggy.

Sorry Zack. I skimmed your post too fast. And I know I shouldn't. You're a bright guy .

 

[gixxerdrew]

There is a twin scroll housing actuator out there that will close off the inside port to the exhaust wheel and as you come up on boost it opens that port for mid and top end flow. That's something that can help every big turbo car.

mostly useful for REALLY big A/R turbine housings though as in 1.0+. In smaller A/Rs your just better off to have a properly designed twin scroll setup. If you tried that with a .58 or similar size you could run into surge issues as well as a nasty curve of dominished returns. I would run that if I had a GT42R car I was trying to street though. I am only aware of it in T4 flange application as well and I think its still preproduction.

Can you go to big on a small turbo? Discuss.

absolutely. I still think I could have done 550-600whp on my 60trim by this exact process. It made excellent pump gas power and was very responsive. Were it not for FPs new HTA technology I wouldnt have wanted to upgrade my turbo at all.

How would a huge intercooler ever HELP spool? When I finally ditched the side-mount for a huge front-mount, my spool rpm went up about 300 rpms.

Turbos can fill volume very fast they blow a huge amount of air. The transient response differences are minute. If you go from 140 degree intake manifold air to 100 degree you make a huge percentage swing in the density, check the ideal gas law. The much more dense air charge coming in is a direct relation to the quantity, energy and velocity of your exhaust gases. (what you need to reduce lag) but there is a balance here as you may have discovered. It depends on the size of your turbo, pressure drop on the IC, and a lot of factors. it can work both for and against you depending on the details. For me it could have been just as much about having a very well designed intake setup and a very nice core for the effect every bit as much as it was the size. I get a total of 4 degree increase in intake temps at the manifold in a 0-175mph 23 second pass in 120 degree ambient at 4000ft altitude. Thats a well running IC setup, IMO. I came to my designs using fluid modeling.

Also, even if running low timing helps spool (which I'm positive it does), the torque is hurt so much with lower timing I don't see how it could be worth it. Your turbo may have spooled at a lower rpm, but you would've gotten to a higher rpm faster anyways with more timing. You got a lower rpm spool, but the guy next to you running more timing is already ahead of you by then!

I played around with this lots, and while it was nice to make the turbo kick in sooner I always came back to the OEM style ramp down of timing at higher boost pressure/MAF frequency. For a couple years I had different maps for different things I messed with. The biggest hit you'll take with a low lag map is in gas mileage. The low timing means your not using your fuel as efficiently you'll end up with a lot more throttle and boost to maintain the same speed on the freeway. I even had one extreme gas mileage map it was so lean I was having problems with my cooling system i had back then and it would drive like shit anywhere except on freeway cruising because it had no accel fueling among other things but I did get 33mpg with it To me the purpose was getting the turbo on quicker is trying to get a broader torque curve but it never happened I just got more noise from the turbo and more energy/fuel being wasted out the tail pipe. Thats my experience anyway, YMMV

 

[soldave]

I run very lean off boost maps (i.e. I am cruising around with AFRs into the mid to high 16s and sometimes touching 17s) which woks wonders for fuel economy. But could it be one of the reasons why my 50-trim seems to be spooling up a little slow.

And here is my timing map, although from 4,500 upwards in the top 3 load levels I need to lean it out and smooth the curves etc. Do you thinking taking timing out when spooling up (1.0 equals no load in this case)?

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[pneumo]

Antilag was invented as a way to spool a turbo without making power.

Use where applicable.

 

[RipperXX]

There's two real types too you know. We hardly have the parts or know how I doubt anyway to use but one type. And thats shit like DSMLink anti-lag which is more for drag racing. Vs something like what a real rally race evo has.

 

[jrohner]

I put the stock timing map back in my car and my spool rpm went from 3100 down to 2700. So now I made a new map, with stockish timing at 3500rpms and under. The stock timing makes my car kinda misfire on the low end with E85 (even with it set fairly lean). I'm goona work on a map to find a happy medium between awful low timing and slower spool.

Before I switched to the FMIC, it spooled at about 2800; I remember having full boost at 2500-2600 back with the stock timing maps and a SMIC.

I haven't really noticed a difference in spool with different AFRs.