VE# for L28ET

[Doug71zt]

Hi - I'm wondering if anyone has a known accurate VE# or Graph with VE vs. RPM for an L28ET or any L series, for that matter. I am looking at compressor sizing for a new turbo and would like to start with accurate numbers on airflow. I know that it's quite variable with different engine combos, but I can make a good estimation if I have some data to work with - IE what the comp ratio, head work, valve size, intake style, etc the engine had. Right now I'm using 80 to 85%, dependant on RPM.

 

 

Thanks - Doug

[Drax240z]

Are you talking VE# on the same engine, without a turbo? A turbo will allow for a VE much higher than 100%.

[Doug71zt]

Yup - N/A VE so I can work it through to a lb/min number. It is for a 3.0 stroker with a ported P90, healthy turbo cam and 8.5 compression. Would desktop dyno be able to model this engine? I've never used it - but am curious.

 

Thanks - Doug

[Drax240z]

Well doug you'll find that the VE varies, A LOT, on RPM. The setup you talk about may reach over 100% VE at a certain RPM, and then reach 60% VE at another RPM. A lot of it has to do with the harmonics of the intake system, and what RPM you get positive pressure waves occuring.

 

I'd just stick with the 80% figure if you want something general to base your turbo sizing on. Or are you building this engine for a specific (narrow) RPM range?

[Doug71zt]

Thanks Richard - If you want to move this thread to the turbo section, it probably has more relevance there.

 

 

Well - I'm attempting to get maximum compressor efficiency in the torque peak range for this next engine, as that's were my current engine will start to ping first as I advance the timing. I am also going ball bearing, so hopefully the new GT compressor maps are accurate enough that I can do this. I was all ready to go GT40 82mm 56trim, but I stepped back and thought about it a bit. As my calculations go, it is too big for the L30. It would be great for an RB26 or RB30 with more RPM potential. That compressor is in it's most efficient range between 6-8K. It's not that efficient between 4-6K where I'm looking for better. I'm accounting for intake losses in the feed to the turbo, IC losses, and was hoping to get an accurate VE number to finish it off. Off the top of my head, I think 80-85 will be close, but it's just a WAG (Wild-A** Guess).

My current favorite compressor setup is a GT37 wheel, in a T04S housing. 76mm, 54 trim, .7 A/R. It fits my HP goals (400ish) and has a nice wide 78 % efficiency area. It also gives me more surge margin, as the GT40 wheel has some problems there.

I guess I am just trying to cover all the bases before spending the big dough. The GT 40 wheel is being touted as the fits-all-engines, world's best wheel, but for what? If I was looking for all topend, and was reving to 8K, I'm sure that it would be the way to go, but for a do-it-all car (daily driver, dragstrip, Mosport) - I think that it would be not the best compromise. Even my T04E 60 trim is too big for the 2.8 - I can induce surge pretty easily. But - I'm learning - max compressor for a stage 3 wheel should be a 50 trim T04E and my 60 trim should have a stage 5 wheel driving it. Knowing what I know now - I would say that the best all-around moderate hybrid would be a T04E 50 trim, .60 A/R with a T3 .63 stage 3 wheel - maybe an .82 on the exhaust for more flow.

When I get it up and running - I'm going to instrument it and datalog - them I will prove or disprove Doug's theory of compressors.

 

Cheers - Doug

[Drax240z]

Alright, moved over for you.

 

I see your dilemma now, and I am curious to how much your airflow numbers are varying based on 80% and 85% VE. I would think you will still be close enough to size your compressor to cover both eventualities. (I think I'd tend towards the 80% number however)

 

This is some good info about turbo's, I think this is the first I've heard of a T04E 60trim being too much with a stage 3 wheel. For my own ride I have been contemplating T04E 50 trim, with 0.60 A/R and T3 0.63A/R and a stage 3 wheel. My issue is I do not want less power available below 3000rpm when compared with the stock T3. How do you find the characteristics of your current hybrid in comparison with the full T3? (I realize it makes a ton more power, I mean drivability, throttle reponse, etc)

[jgkurz]

Drax, I had a T04E 50 trim compressor with a .63 turbine housing and stage III wheel on my L28 3.0L. I was very happy with the power to lag ratio. On a Mustang dyno I made 310RWHP with a poor tune and had very little lag. The 310RWHP was at 13psi. If the AFR's were correct I could have made MUCH more power. The compressor map for the 50 trim wheel is among the most efficient of the TO4 wheels. From what I understand, Jim Wolf Technology uses that the same wheel in their Sport 400 turbo for the L28. I've since upgraded to a larger turbo for more potential peak HP. With the upgrade I have definately added more lag.

[mobythevan]

One problem with providing an accurate VE table for the engine is that the fuel delivery must be exact for the VE table to be exact. I am just talking from MS experience here, but if my injectors open close time is not exactly what I tell the ECU or fuel delivery is off a little then a tuned VE table will be off a little to compensate. Not sure how accurate of numbers your looking for, I could send you my table and if it doesn't correlate to others you could just toss it. Maybe if you got 3 or 4 tables from some of us you could compare and come up with an better guestimate.