Compressor vs turbine wheel spool

[Ethan92GSX]

Unfortunately I have to post this in the newbie section because I haven't posted on tuners before but hopefully it wont matter. I am currently running a PTE 5457HP turbo which has been amazing except for the fact that it seems ridiculously laggy. Everyone says it should spool like a 16g and hit full boost around 3800rpm.

The only way I can hit full boost at about 4000 rpm is in 5th gear. 1st gear is 7000rpm, 2nd is 5800rpm, 3rd is 5300. I have been attributing this to a cheaply rebuilt stock block with low compression (about 120psi in all 4 cylinders). I have ran a leakdown test and it came back as 20-30% leak all through the rings, but i'm still able to hit 110 trap speeds so I haven't really worried about it until now.

So I have a few questions, my first question is does this thread have anything to do with my turbo or is it only talking about compressor wheels http://www.dsmtuners.com/forums/turbo-system-tech/404033-garrett-57-trim-s.html

My second question is, could my low compression be the cause of my spool problems.

Third, what affects spool more compressor wheel size or turbine wheel size. I plan on going for a slightly bigger setup and I have a lot of compressor wheels to choose from with my current turbine wheel (5557,5757,5857,5957,6157), but I don't want to waste my money if a 6262 will spool almost the same as a 6157 or if the problem with the 57 trims as shown in the link above is my problem.

My last question is, is it possible to send PTE my turbo and say i want it rebuilt from a 5457 into a 6157 for example without having to pay the price of a new turbo.

I have done all the basic checks, no boost leaks, no exhaust leaks, and I know the wastegate is staying closed until full boost because I have an o2 dump.

 

[H@xtGSX]

Well I don't have much experience with a turbo that big on these cars, but I think I can somewhat address a couple of your questions. I am no pro, but this is what I've seen.

Yes, compression *can* affect spool. Not to a huge degree if it's anywhere near spec, but it can make the difference of a few 100 rpm. Anything you lose from the compressor side isn't spinning the turbine upon exit. Really though, unless you're blowing a ridiculous amount of crud out of your PCV, I doubt it is having a major effect.

For the question of spool speed, from what I've seen on Cummins diesels, the turbine side had the greatest effect on speed of spool. Now there's a balance trade off when you start messing with the wheel ratios though, and basically what the compressor sends thru the intake ultimately determines how fast the turbine is pushed... conversely, the turbine must get to speed to increase the exhaust pressure. Get too far out of whack with either side and spool time is usually decreased to a degree. From working on a hx40 on a truck though, a slightly larger turbine tended to increase spool speed by several hundred rpm. Remember, it's all about VOLUME. These 2.0's don't have a hell of a lot of volume to work with when used with bigger turbos, so if the turbine side can catch a little more force than the compressor is scooping up, spool *should* increase... I have seen instances where that wasn't the case, but they were set ups done by amateurs who didn't bother to do their homework before slapping a semi truck turbo on a 2.2 L motor... (H22, go figure)

 

[JusMX141]

Your turbine wheel / housing choice should be made based on your engine's displacement, boost level you're planning on running, and obviously the compressor you're running. For example, the Small 16G, Big 16G, 18G, 20G, and 68HTA all use the same turbine wheel and housing but have drasically different spool characteristics.

I don't know enough about what PTE's now calling the "57" turbine to tell you if it would work well paired with a 61mm (35R) compressor. My guess would be that it's a bad idea- at some point you're going to run into a brick wall with turbine flow before the compressor has reached it's flow potential.



Not reaching full boost in 1st until almost redline is not that big of a concern as some cars with large turbos never even open the wastegate in first- but your 5457 is far from being considered an enormous turbo which wouldn't reach full boost in the lower gears. I think you have a problem somewhere- if you're sure there are no boost or exhaust leaks, start checking your base timing and valve timing.

 

[Ethan92GSX]

I don't have a PCV valve I'm running both crankcase vents into a catchcan. My base timing is set at 5*, and my valve/crank timing is perfect. I have adjustable cam gears and I have tried to go less overlap/more overlap and it has absolutely no effect on the cars power or spool based off dsmlink it makes no sense.

I don't think PTE would sell a 6157 if it didn't function correctly, im just curious how much extra lag it would have over the 5457. I usually run 22psi and occasionally bring it up to 30psi on race gas.

The main reason I'm blaming the block is because of the 30% leakdown, when I would pressurize the cylinder to 50psi I could feel and hear the air coming out of the dipstick. I'm thinking a lot of the exhaust pressure is being lost through the rings and I have to be at high rpms in order to push it out fast enough that it wont have time to leak much. Also on top of that just in the last couple weeks my car has started to have blue smoke poor out of the exhaust after boosting it hard and letting it idle. The turbo has 0 shaft play so the only thing it can really be is the rings since the valve stem seals are brand new.

 

[JusMX141]

I don't think PTE would sell a 6157 if it didn't function correctly

That's a good one.

PTE does zero R&D....they just build shit. A perfect example of this was a SCM6031E used on a friend's car a while back...logged a max airflow of 48 lb/min @ 30psi with the DSM bolt-on turbine housing. That's pitiful. A 20G can perform almost as good while spooling about 500rpms sooner. Swapping to a T3 .82 turbine housing allowed the turbo to breathe to it's potential.

The point is if that particular turbo performed so poorly, why does PTE even offer it?

 

[Ethan92GSX]

That's a good one.

PTE does zero R&D....they just build shit. A perfect example of this was a SCM6031E used on a friend's car a while back...logged a max airflow of 48 lb/min @ 30psi with the DSM bolt-on turbine housing. That's pitiful. A 20G can perform almost as good while spooling about 500rpms sooner. Swapping to a T3 .82 turbine housing allowed the turbo to breathe to it's potential.

The point is if that particular turbo performed so poorly, why does PTE even offer it?

Well they must have at least tested its flow capabilities in order to make a horsepower estimate. I did a search on the SCM6031E and found a bunch of people saying it was an amazing turbo so it might just be the luck of the draw idk. That stock dsm housing might have been a bottleneck on the airflow.

 

[Pauls99Gst]

Hey sorry is the turbo ball bearing? Because I had a problem with spool with a PTE ball bearing turbo because I was running to much oil pressure to the turbo.

 

[Ethan92GSX]

Hey sorry is the turbo ball bearing? Because I had a problem with spool with a PTE ball bearing turbo because I was running to much oil pressure to the turbo.

No, its a journal bearing in a T04E housing.

 

[JusMX141]

Well they must have at least tested its flow capabilities in order to make a horsepower estimate.

They estimate horsepower based on the amount of airflow the compressor and cover will generate with no regard to the turbine side whatsoever. This is also a company that offers a SCM6027E, which is a 60-1 compressor paired to a T327 (Stage 2) turbine (not much bigger than a TD05H) in their DSM bolt-on turbine housing. Talk about bottleneck.

I did a search on the SCM6031E and found a bunch of people saying it was an amazing turbo so it might just be the luck of the draw idk. That stock dsm housing might have been a bottleneck on the airflow.

It's a 60-1 compressor paired to a T31 turbine...the same wheel combination is available from a variety of vendors but is considered old tech by today's standards.

Obviously the turbine housing was the bottleneck- my point is that wheel combination should have never been offered with such a restrictive turbine housing....and had the company done research on the turbos they build, they would already have this figured out.


Back to the original topic- if you think your 5457 is laggy you're going to hate a 6157.

 

[LandoAWD]

I find it odd that his spool numbers nearly match mine, despite the downsize.

Jus: You PTE hater, you. You and Andrew should have a picnic.

 

[Ethan92GSX]

Ok so don't put a huge compressor on a small turbine that sounds fairly straight forward. So does going larger on the compressor and turbine both slow spool? And which one usually slows it down more? From what H@xt is saying I take it having a larger turbine wheel than the compressor causes quicker spool? that sounds odd to me though.

I should also add that I'm running a .63 AR not the .48 AR but I don't think that's supposed to make my spool this bad.

 

[JusMX141]

I find it odd that his spool numbers nearly match mine, despite the downsize.

He most likely has a problem somewhere- you don't.

Jus: You PTE hater, you. You and Andrew should have a picnic.

Oh I don't hate them- they've been funding every car part I've purchased since 2005.

I just hate seeing good people spend good money on bad products from a company with a reputation of being unreliable.

Honestly, with all of the options out there today, PTE really has to step up the game on journal bearing reliability or do a little more R&D on their turbine housings if they want to compete with companies like Forced Performance as far as bolt-on turbos go. Their turbos like the ball bearing T3 6262 are making serious power, but throw a DSM bolt-on turbine housing on it and it becomes a turd. A FP 3065, DSM 82, or even a HX40 in a DSM bolt-on housing would walk all over it in terms of total airflow production.

So does going larger on the compressor and turbine both slow spool? And which one usually slows it down more? From what H@xt is saying I take it having a larger turbine wheel than the compressor causes quicker spool? that sounds odd to me though.

Larger rotating assemblies slow spool and boost recovery, yes. So does a larger a/r turbine housing. It's a delicate balance between finding a setup that flows the best and spools the quickest- you can't really pinpoint the compressor or turbine being a huge contributor, but an unbalanced setup (in terms of airflow) is going to be inefficient and unreliable as well.

Too large of a compressor on too small of a turbine will MELT thrust plates and cause more load on the journal bearings than normal. This is because the smaller turbine turns faster and will often spin a certain compressor wheel faster than it's designed to be used, resulting in extreme thrust loads.

On the other end of the stick, an excessively large turbine will cause a certain compressor wheel to spin too slowly and not achieve the total airflow for which it's designed. If you put a 14B compressor on a Garrett P-Trim turbine (huge), you're now spinning the compressor about 50k slower than it was designed to be used on a TD05H turbine....so less airflow is going to be produced no matter what boost level you're running.

This is why companies who are assembling turbos or building hybrids without doing extensive R&D on each one are just shooting themselves in the foot.