[charlie66]

Hi everyone , I finally got a chance to dyno my turbo charged 194.5 ci 4 cylinder this passed week. I tried 30 psi 34 psi 38 psi and 40psi. The results were: @ 30-549 hp 34-606 hp 38-616 hp and 40-612 hp. These numbers are at the back tire not the flywheel..

The car is a 1964 Tempest lemans . It has a turbo 400 with a 9" rear 3:50 ratio with mickey pro drag radials.

As you can see the jump from 34 psi to 40 was only 6 hp. So I went out the other day and checked the exhaust back pressure and this is what I found:

@ 30 back pressure is 38.Thats 1.26 ratio. 8+ more psi .Air temp went from 50-148=98 rise

35 psi BP was 46 11+ more. Ratio 1.31 Air temp 57-162 105 rise. 7 more then 30 psi run.

39.4 psi BP 56 18+ more . 1.43 ratio. Air temp 51-170= 119 rise.

The turbo is a 76mm with a .68 A/R . I have a .81 A/R that I just installed but still have to check the BP.

If this doesn't fix the problem I will check the pressure differential before and after the intercooler just to make sure the turbo is in range with what it should be.

The fuel being used is e85.

__________________

[johnta1]

Nice!

Good power from a 4 cylinder.

What size is the exhaust system?



PS: 3.15 HP/CID awesome power.
(from wheel HP)

[charlie66]

Thank you.
Its 2 1/2 to the turbo and 3 1/2 out the back..

[charlie66]

What is the general rule of thumb with the percentage drop in hp with a turbo 400 and a 9" rear? Im trying to figure a ball park hp number its making at the crank. 22% says 770 hp..

[charlie66]

I just read your P.S. I never thought of that.

Thank you...

[PAUL K]

Good job and interesting information ! Thanks for sharing.

[OCMDGTO]

That's incredible! You are embarrassing us V8 guys!

[ponjohn]

What does this car run in the 1/4?

[charlie66]

Originally Posted by PAUL K

Good job and interesting information ! Thanks for sharing.

Thank you.

You're welcome. I'm trying real hard to figure out all the bugs I have had. I've come along way in doing so, so far , but still have a few still remaining, like the back pressure one.

[charlie66]

Originally Posted by OCMDGTO

That's incredible! You are embarrassing us V8 guys!

Lol, Thank you.

All you have to do is turn the boost up to fix that . Hahaha..

Being this motor is half of a 389 , I think it would be safe to say a 389 would have made close to 1200 hp at the wheels at the same boost level.....

[Tom Vaught]

Charlie, Steve Morris who does a lot of BB Chevy Boosted Engines was running a similar test on a Detroit Area 509 CID "street car" when I was at his shop one time.

The boost pressure went up in the intake manifold but the engine did not make the expected extra power.

Steve eventually ordered a different intercooler for his dyno and the engine went back on the dyno.

Now the 509 engine made over 2000 hp vs being stuck around 1750 HP.

This was due to an inlet restriction before the heads. In his case it was the dyno intercooler. In your case it might be the throttle body, intake runners, or actual intake ports themselves. So what you observed is very possible.

Tom V.

[charlie66]

Originally Posted by ponjohn

What does this car run in the 1/4?

I don't know yet. I will need a roll bar first I think or I would get kicked off. I think if i could get a 1.3 60ft it would go 9's. It feels real good I can say that...

[BruceWilkie]

How big is your waste gate? IMO your intake temp rise seems in line with psi increase but I haven't done the math. Your backpressure appears to be choking the motor. A larger a/r may help on top end but at the sacrifice of spool up. A larger gate and/or exhaust MIGHT be a better solution. Compare turbine inlet pressure to outlet pressure. A large expansion immediately off the turbine and run for some distance before gradually necking down to 3.5 may help. It appears your not letting out what wants to get in. Hence the boost increase and minimal gains.
You wouldn't see a boost increase if the turbine wheel didn't supply enough drive. Fwiw lowering IAT with greater intercooling capacity is a good place to find more power.

That said, you can't put in what doesn't come out.

[Tom Vaught]

My post above was based on the actual flow capability of the inter-cooler (not the cooling efficiency) was what was causing the PSI gain with no HP increase.

In Charlies case he is reading at the intake manifold so the exhaust restriction makes the most sense, as you mentioned. Bruce.

Tom V.

[charlie66]

Originally Posted by Tom Vaught

Charlie, Steve Morris who does a lot of BB Chevy Boosted Engines was running a similar test on a Detroit Area 509 CID "street car" when I was at his shop one time.

The boost pressure went up in the intake manifold but the engine did not make the expected extra power.

Steve eventually ordered a different intercooler for his dyno and the engine went back on the dyno.

Now the 509 engine made over 2000 hp vs being stuck around 1750 HP.

This was due to an inlet restriction before the heads. In his case it was the dyno intercooler. In your case it might be the throttle body, intake runners, or actual intake ports themselves. So what you observed is very possible.

Tom V.

Hi Tom,

So I guess now its all about finding out what's causing this choke point im seeing. What do you think about the possibility of it being from the exhaust housing ? The throttle body I have on it now is a 75 mm. What size would you think it would need to be in my case @ 40 psi?

I was thinking that it might be the intercooler. That will be my next place the check. If the turbo is making 50 psi and its coming out of the cooler at 40 psi im sure the turbo at this point will be very unhappy right?

P.S. Tom , I want to thank You for all of the help you have given since day one. You have been a wealth of great information for me through this whole build between you sizing the turbo and tolerating all my phone calls to you filled with questions....

[charlie66]

Originally Posted by BruceWilkie

How big is your waste gate? IMO your intake temp rise seems in line with psi increase but I haven't done the math. Your backpressure appears to be choking the motor. A larger a/r may help on top end but at the sacrifice of spool up. A larger gate and/or exhaust MIGHT be a better solution. Compare turbine inlet pressure to outlet pressure. A large expansion immediately off the turbine and run for some distance before gradually necking down to 3.5 may help. It appears your not letting out what wants to get in. Hence the boost increase and minimal gains.
You wouldn't see a boost increase if the turbine wheel didn't supply enough drive. Fwiw lowering IAT with greater intercooling capacity is a good place to find more power.

That said, you can't put in what doesn't come out.

Hi Bruce. Its 44mm's and water cooled..

[charlie66]

Originally Posted by BruceWilkie

How big is your waste gate? IMO your intake temp rise seems in line with psi increase but I haven't done the math. Your backpressure appears to be choking the motor. A larger a/r may help on top end but at the sacrifice of spool up. A larger gate and/or exhaust MIGHT be a better solution. Compare turbine inlet pressure to outlet pressure. A large expansion immediately off the turbine and run for some distance before gradually necking down to 3.5 may help. It appears your not letting out what wants to get in. Hence the boost increase and minimal gains.
You wouldn't see a boost increase if the turbine wheel didn't supply enough drive. Fwiw lowering IAT with greater intercooling capacity is a good place to find more power.

That said, you can't put in what doesn't come out.

I have a 3 1/2 outlet pipe that is 4' long.

[Drag Star Le Mans]

Way to make us 195 owners proud!!! Now i'm going to watch some of your old burnout videos

[70 bird]

Great numbers!! and thank you for posting the bp readings.

[Tom Vaught]

Originally Posted by charlie66

Hi Tom,

So I guess now its all about finding out what's causing this choke point im seeing. What do you think about the possibility of it being from the exhaust housing ? The throttle body I have on it now is a 75 mm. What size would you think it would need to be in my case @ 40 psi?

I was thinking that it might be the intercooler. That will be my next place the check. If the turbo is making 50 psi and its coming out of the cooler at 40 psi im sure the turbo at this point will be very unhappy right?



P.S. Tom , I want to thank You for all of the help you have given since day one. You have been a wealth of great information for me through this whole build between you sizing the turbo and tolerating all my phone calls to you filled with questions....

Did you swap the Turbo exhaust Housing that Dave originally recommended or did you keep it. It was a larger A/R housing that I believe he suggested in the beginning, not as much bottom end response but more top end.

Most guys running the same boost pressure that you are with a V-8 engine are running at least 90mm throttle bodies and i believe Brian H is running a 105mm throttle body. The pressure into the manifold may still be 35-40 psi but the actual mass flow into the engine may be restricted by the throttle body.

You are right on tract with that assumption Charlie. most assume a 1.5-2.0 pressure drop across an intercooler is acceptable, in your example a 10 psi difference would say the intercooler is restricting flow a great deal.

I will say that you never gave up Charlie, from the beginning.
With the blow thru carb stuff and the mods you made to the carb.
With the plumbing changes.
With the exhaust changes.
With the switch to EFI and you learning all about how to tune a boosted EFI engine
With the Fire in your work area and you saving your engine stuff.

You have done really well for yourself and I am very proud of you and your efforts with making a very fast/powerful 4 cylinder engine at high boost pressures for a street car.

Keep up the good work Charlie.

Tom V.