mr2racer7

I am curious on what you guys are getting for back pressure to boost ratio. I would like to know from stock to the insane combination. Please let me know what your set up is like, such as cams, exhaust manifold, turbo, A/R on the turbo, HP. It would be great if you had a dyno graph as well. Thankyou

mr2racer7

Nothing since July 31, 2009? I mean no one here ever measures back pressure to boost ratio? I know there are some smart people out here.

Stockie

iTrader: (11)

Ohkay nvm

mr2racer7

I forgot to mention that i would like to see real answers that would help out the community.

cij911

iTrader: (14)

Buschur did....The posts are really really old...Are you trying to figure out what to do and what boost to run ? If so, those have been addressed a billion times as well. If you are just curious what back-pressure data has been recorded with different configurations (somewhat pointless), then you'll have a hard time....G/L

240Z TwinTurbo

iTrader: (25)

If my memory serves me you don't want to exceed 1.5:1 exhaust:intake ratio. I had a few buddies in the early 2000's measuring back pressure on Zcars at boost levels of 22psi and they were seeing ~25psi of back pressure before the turbo. I am not sure you can have less back pressure than boost, but perhaps it is?

03whitegsr

iTrader: (8)

It's not something that really matters to the guy that already has a turbo and doesn't intending on swapping turbos out like they change their underwear.

The guys that are competitive and do measure that kind of stuff aren't going to post it.

You might be able to get it out of companies like FP that do take those measurements for developing consumer products though?

mr2racer7

I understand that there will be different results for different engine combinations. I realize that the people most likely to measure exhaust back pressure to boost ratio are going to be the top dogs. It will be then real easy to find out about there combination since they normally post it all up on here.

I want to see what turbo they are running and what kind of back pressure they are running. Its a good way to gauge the efficiency of the turbo set up for the motor.

RSMike

iTrader: (1)

check this build out.

http://www.mmc.org.nz/forum/viewtopi...449&highlight=

there is a section in there that talks about the exhaust manifold to boost ratio, talking about how when you start to get higher boost pressure than exhaust manifold pressure, the exhaust manifold starts to work like a NA car and equal long length runners work better.

Cheers, Mike

mr2racer7

Yeah that is basically what i am going for. I am really curious on to what the top guys are getting when they use turbos like a gt40, gt42, 6262, 6265, and 6765. I see the crave about the PTE billet turbos making a lot of power but still on T3 exhaust sides. I would love to see what those guys are getting for exhaust back pressure to boost ratio, compared to the gt40 and gt42 guys.

I figured that there will probably not be that mush testing. thank you guys for all the helpful information and links.

vigge

Dont know if this is any help, but here are boost/ back pressure /Tq and Bhp curves from my 2.0l dyno run . Pressure readings as absolute pressure
http://www.stcf.net/ProjectX/run3_4.jpg
Turbo holset HX40super, turbine housing #18, EWG 60mm, 272/10.4 Cams

mr2racer7

Yeah that does help. Looks like a pretty good combination. It seems to breath real well in the lower rpm's with quick spool, yet still retains good torque all the way to 7500. I will guess past 7,5000 that the turbo has run out of air.

vigge

Yes the compressor began to be out of breath at higher revs as well as the rest of that engine, hydraulic lifters, cams etc.
Spool on that log is a somewhat delayd compared to road runs due to the rapid inertia dyno sweep. Turbo was previously with #14 housing, spool 200-300rpm lower, but "died" out as as much sooner in high end also.
On road spool 4th gear with 14 housing, in two different abient temps
http://www.stcf.net/ProjectX/spoolia_14pesalla.jpg
3rd gear
http://www.stcf.net/ProjectX/spoolia_14pesalla_3.jpg

18 housing curves with 200-300rpm off-set to above