Turbo advice

[jgkurz]

Thanks,

 

I'll have to see if I can spot any numbers on it. I got this one because the price was good and Hugh talked me into it, but I'm not opposed to selling it and getting a .63 or something more correct. I haven't built the engine yet so I can tailor it to whichever turbo I end up with. Since you're local to me, maybe you might be able to look at this turbo and tell me what it is that I have one of these days?

 

Greg

 

Sure, but sending me pics would be quick and easy. Just PM me if you have any available that I can look at.

[Soundmasterg]

Sure, but sending me pics would be quick and easy. Just PM me if you have any available that I can look at.

 

 

I just took some pics and I'll PM you. Thanks!

 

Greg

[flames_187]

Hey Jeff, What boost level were you running with this setup?

Thanks

 

 

i believe he was at 20psi...

[jeffp]

First of all I have completed 5 setups on the turbo. I will talk about the TO4E setups.

 

The fallacy that a smaller exhaust turbine housing is better might be true for a stock car running 7psi of boost and has a power band to about 4500-5000 rpm's. YOU WILL NEVER GO WRONG WITH A BETTER BREATHING ENGINE. That being said I will explain. You can get turbine housings from about .48 A/R .63 A/R .70 A/R .82 A/R and I believe 1.06 A/R (I have NEVER had need of a 1.06 A/R eahaust turbine housing) You need to size the exhaust turbine housing correctly for - RPM, HP, CAM, exhaust, static compression ratio, and for the desired power band.

The idea of back pressure on the system is also misunderstood as well. The best rule of thumb is to make the turbo exhaust turbine the bottle neck in the system, not the exhaust system.

The .63 A/R turbine housing with the stage 5 opening is the very best option for an engine that will run into the 7K rpm range. the .48 housing is good for an engine that makes power to about 5K rpm. so there are your choices for a good setup.

The .82 A/R housing is best utilized for the engine that is making 650hp and higher, you will the spool rpm by about 300-450 rpm and spool later.

My TO4E turbo with the stage 5 exhaust was well into spool @ 3400 rpm's that most here state. I could run down the road in second, take the engine to 3K and hold it there, when I tagged the throttle the turbo went to 23psi, no lag, no delay, to speak of. What a change in power, as I said it was almost uncontrolable. I don't really know why most of you get spool at 3400-3500 rpm's, that is a slow spool.

I ran that turbo to 500Hp(@ the crank) and it was done! My next setup after the TO4E was a modified TO4E turbo running a 62-1 compressor. I also had a .70 A/R exhaust turbine housing. I lost spool and it went to about 3400 rpm's, easier to control the car that way. That setup got me past 550hp, and I ran that unit to 27psi of boost. I never got to dyno that setup, as it was on the car a short time. So even the .70 A/R housing moved the spool rpm up higher then the .63 A/R unit.

I did do the back pressure testing on the TO4E setup, and @ 25psi of boost @ 7K rpm's I had 25psi of back pressure @ the inlet to the turbo. I did not even go to crossover conditions on the exhaust.

Also, I have here or read somewhere that back pressure of 2 times the turbo pressure is acceptable. Hogwash! you keep the back pressure as low as you can period! once you have surpassed the boost pressure, you will NOT make any more power. The air/exhaust is going to flow, one way or the other it is going to move somewhere, so if you have high back pressure on the exhaust, then the ONLY place for the pressure to get released is up the intake, make no mistake, reversion is very real, and it is a performance KILLER.

The .63 A/R turbine housing is the very best for an engine running 650Hp VERIFIED! The static compression ratio will determind how much boost you will need for the desired power, and the cam will also affect the compression ratio as well.

Now the setup is the GT series garret turbo. GT35R with the .63 A/R exhaust turbine housing. This turbo if you look at the compressor map is a much larger turbo then the TO4E. I spool now @ 3200 RPM's and the car is much more controlable. The engine also makes 658Hp @ 509 foot pounds, that was on a dyno-jet, I think the Mustang dyno would read lower.

I topped out @ 22psi of boost, and on the dyno, going from 22psi to 26psi made no Hp increases. So I either have a restricted exhaust system, or the .63 A/R housing is to small. I haven't taken the time to do the testing to determine which is the case. I suspect it is both the housing, and the exhaust system.

TURBO CAMS, whoever said a good N/A cam was bad for a turbo car is full of BULL! I would be willing to say that MOST people know very little about cam dynamics and how they will affect the operation of an engine. I have even read a number of articles from known published authors, and cam people like Racer Brown that could not tell me what would happen to an engine running this cam or that cam for a turbo engine. Lets just say that the cam will affect the reline of an engine more then it will affect a turbo, I realize there are other variables to consider as there are some that just go crazy with duration, lift and the whole thing that will take a good build and make the engine a dog because of improper cam selection.

I haven't published all of my testing data, but what I have posted will work for just about anyone here wanting to make power with the L engine. I can tell you another thing, the high Hp engines here are a short lived peek power due to heating, not much more then two pulls on the dyno within a few minutes of each other and the engine is to hot to run again until it cools off.

I have listened to a good deal of opinions here and elseware on the topic, only to find like you most of what is being said are statements of opinion not backed up with the data, but rather from what they heard. I got tired of spending money only to find the results were very different then I expected. I have spent thousands and thousands of dollars to finally put an end to the opinions and speculation. I have the hard line data and I know EXACTLY where I need to go or do to get my desired results, no guess work, just raw data. So there you have it. I could still do further testing of my setup, but at this point I have other worries to contend with like over heating, and until I resolve those issues turbo selection is last on the list.

[Zmanco]

jeffp, thanks for sharing your experiences - that's the kind of feedback I'm looking for. At this point I'm leaning towards a T3/T4OE with stage 5 .63 AR turbine and .50 trim compressor. To recap, my goals are to make power through 6500 rpm and around 275 WHP. The cam is a Schneider turbo grind with the following specs:

 

Intake Duration (gross): 270

Exhaust Duration (gross): 260

Intake Duration (.050”): 230

Exhaust Duration (.050”): 220

Intake Valve Lift*: .460"

Exhaust Valve Lift*: .460"

Lobe Separation: 114

 

Question 1: I can't find any discussion about the differences between a stage III and V turbine wheel, but it appears the V is bigger. What trim would your recommend for the turbine?

 

Question 2: From what I've read, it doesn't seem that the AR matters much for the compressor. Still, since I'm going to buy a turbo built to my specs, what should I choose?

 

Thanks in advance!

[jeffp]

Calculate the required air flow that the engine will require to get the desired hp. Then take a look at the compressor maps to find the best match for your goals. You will need to know swept volume of each cylinder. Then you will need to calculate the pressure ratio for each cylinder that will get you to the desired hp and multiply that by 6 then you will have a very good idea of what you will need.

I don't recall off the top of my head, but the calculation is out there, and if not get a book by John Lawler engine math book and all the formulas will be there you will ever need to design a engine application.

[Zmanco]

jeffp, I've done all the calculations and the T3/T04E .50 trim map fits the best. However, none of the maps specify the other specs, such as AR for either side, trim for the turbine, stage of the turbine, etc. I'm a little surprised how much of choosing a turbo remains a black art.

 

BTW, does anyone have a source for Garrett turbos they can recommend? The local place here in CO can't get them with a stage V wheel, and the other place several have recommended, speedshopthagard.com, is out of business. I've found a few via google but hate to spend that kind of money on a site that I know nothing about.