M Versloot

Hi. Just want some advice on why my turbo won't boost higher than 35psi.

My setup;
B18B Benson block with 84mm CP pistons. (9.8:1) Pauter rods
JG 296/300T cams and valve train kit
Custom exhaust manifold (Chuck Seitsinger copy)
Turbonetics T72 with Q-trim and 1.00 exhaust housing
Edelbrock intake with 70mm throttle

It's a full drag car and it's running on methanol. Car made 730hp with 32psi.
Car with driver is 2200 and best time is 9.70 with 155mph.

The car will not boost any higher than 35psi with waste-gate fully closed.
We are about 4000 feet above sea level.

m R g S r

how do you know the WG is fully closed? It sounds like the WG is opening up.... Maybe spring isn't stiff enough?

C2K_TB_TEC

Niiice setup, Mr Versloot..

Maybe get the turbo balanced and checked : )

At around 730whp It could be around 830-850hp on the fly..
Looking at the T72 comp map, it seems that you "probably" running out of compressor..
How volumetricly efficient is the 2lt?
What rpm with the current cam spec, headflow, mani... etc will it take to go more than 35psi?



Do you think you need more rpm? At what rpm does the car reach 35psi? Maybe enhance engine flow / VE, above that rpm..
If so, will the engine support the exh flow and pressure needed to get the desired pressure ratio, if you rev higher?

Does the current cams support what is needed, maybe adjusting the cam timing could help..?

BTW, Only trying to help : )
Im a theorist as you know, so mind my nooobness when it comes to practical...

Bugermass

does it hold s teady 35 or does it fall off at higher RPMs?? Being that high up (elevation) I'm leaning twords turbos out of breath.. You MAY be able to get some more power outta it with cam timing adjustments.. Depends how high your reving and how much boost your loosing through the overlap period. We made a little over 600 on a stock sleeve piston and rod LS on Q16 @ 26PSI and 75 shot on a big SC61 with some custom cams we have, but we're at sea level. So it seems about right for 4000Ft ..

redflaredcrx90

damm isnt 730hp enough power

BubsBoostedEG

i had similar problem waste gate was blowing open, changed spring and went from 29psi to 33psi

extremeracer

Hi -fellow South African Honda drag racer's

We are actually at between 5000 and 5500 ft elevation - very similar to Denver, Colorado for you guys in the US.

The atmospheric pressure is 12.4 psi

Thus the pressure ratio at 35 psi is 3.82 assuming no pressure loss in the system (so in essence it could be closer to 4.00 with pressure loss factored in) and not 3.4

Now plot 4.0 PR @ 85lb/min and see where you end up in the map and you'll see its on the edge of the map and not very efficient any more !!

The high altitude IMO has a significant impact on the available boost and corresponding flow !

If you were at sea level it would be much easier to run the compressor closer to its peak mass flow !!

There is a car on here that has made 800whp (according to them) with a T72 - but that would be at lower elevation, thus lower PR, thus lower down in the compressor map, thus higher effieciency.

I know I used thus alot - LOL

extremeracer

BUMP for results

Please chime in on your experiences and/or suggestions

From previous tests on the OP's car - the wastegate doesn't seem to be leaking

It has the hardest available spring installed with maximum preload (bolt on top) and is pressurised on the top port

C2K_TB_TEC

BUMP to the fastest FWD Honda in S.A - I think its a lil more than 730whp..

Hey TONY, waaassuuup?? : )

To all the Honda gurus, what do you guys think?

miller

The DA could be a huge factor along with other things.

A few good points have been brought up already. Are you logging back pressure, shaft speed? What other data do you have that we can go by to diagnose what you have going on?

extremeracer

@miller: I dnt think he has any other data - such as shaft speed -

Theoretically the backpressure (at least from the Turbo side of the equation) shouldn't be a factor - as he is running a 1.00 T4 Turbine housing with the Q trim wheel

Would the cam timing and valve timing have such a big effect - and what could the cause be ??

Just as a reference - on my setup Im currently making 28 psi @ 70% duty cycle on the Blitz boost controller with a T66 0.70 P-trim (smaller compressor, smaller Turb. housing, smaller Turb. wheel)

Therefore using a simple equation it should be capable of 40 psi @ 100% in theory

On his car he is only getting 35psi maximum with the wastegate fully closed
Im getting 28 psi at only 70% of the Turbo capacity

This is at the same track , same conditions

That leads me to believe that it is possibly a cam/valve timing issue

What are your feelings on this ???

TheShodan

iTrader: (14)

This is honestly one of the most thought out threads I've seen in a while. Solving a problem using information, a cool head, and an actual testimonial. Keep it up.. I'm just enjoying the information

extremeracer

Any other thoughts - help plz !!

dvst8r

I would try feeding the top port on the wastegate with drive pressure to see if it would keep it closed, my guess is a leaking wastegate. We see this quite often in the diesel world where guys are running compounded turbo's in excess of 100psi.

Honda_Mad

Coz u need a Bullseye ETT S372 with race cover like the Nascar Opel!!lol

Joke's aside! Big Up Mr Versloot + Extreme racer- Doing use Honda guys proud in SA.

extremeracer

Any other thoughts - or similar experiences ????

@Honda Mad a S372R im sure is on the wish list for both of us :-) - but we'll have to make do with our Old School Turbonetics !!!

boosted91crx

Just sounds like the turbo is maxed out regardless of what the map is saying.