darkphantom

iTrader: (2)

ive noticed on alot of dynos where the car gets full boost around 4-5rpm on a single turbo. and how AROUND 6-7RPM REACHES FULL POWER. however on some cars the power starts to drop after 6500-7500rpm, one of the reasons is because the loss of boost at a high rpm..



my question is this. is there a way for a car to properly hold boost at a high range after the power is reached (example a car having a peak power at 6000rpm but after 6k the power is dropped due to loss of rpm)


the only smooth rpm ive seen is on a corvette. at 4k the power is reached but with a straight line till 6k.




IS THAT BASED on the tunning, the way the motor is built?

just curious what makes a car able to hold the boost (powerband) after the peak power

TechTrix

iTrader: (2)

those are both piston motors. you cant say that it lost boost pressure at high rpms because there is no boost map on the dyno sheet. usualy you see power drop after certain rpm because parts like the head, or intake, or exhaust cant flow anymore and there restricting the engine... on that first dyno sheet, the curve is wonderful, you have 375+ hp from 4500-6500rpm, and great tourqe also...

darkphantom

iTrader: (2)

The Reason Why I Was Asking Is My Power Is Great Around 4-6 But On A 1/2 Bridge Your Supposed To Rev The Hell Out Of It Because Of His Port. So Im Wondering Whats Going On. Also I Had To Take Apart The Motor Since The End Housing Was Cracked Luckly I Found That Before It Happened

Nihilanthic

First one is a 2.3 with home ported heads and a holset from a diesel. I forget which cam, prolly just a FMS A237.. nothing fancy. Really high psi though (30 or so) because the head flow is pretty mediocre and you need high pressure to shove air through those heads.

Anyway, "Boost at all rpms" is a misnomer. That doesnt mean you have a big powerband. If you want "boost at all rpms" then you need to get a supercharger - period. But that will still give a peaky powerband because then you basically just shove the torque curve up.

If you want a big powerband, which is flat power, then just select your turbo well, or get a bigger motor with a mild cam, or a stock/street ported 20b if you want to stay rotary.

Old Slow Coach

If power is dropping off due to the turbo running out of breath, then I think you can solve that problem by swapping in a different turbo that can deliver more air, at the same efficiency level. No?

darkphantom

iTrader: (2)

i got a t78

this is my dyno



V8KILA's dyno has had continus poweband on his dyno the whole way through so thats why i was asking





see how his stays smooth the whole way while mines start to drop

im thinking it might be the port

Old Slow Coach

OK... your problem is not that your turbo is running out of breath. T-78 can deliver more than enough volume of air to support higher power than your peak. You mentioned something about "loss of boost at high rpm"... can you elaborate on that? What exactly were your boost gauge observations across your rpm range?

crispeed

You can't compare dynos unless you know for certain what the boost were. For example on V8 killa's dyno sheet with the 'red line' the boost peaked at 36psi at 6K rpm and dropped to 32.5psi by 6.5k rpm and at 7.7k rpm it further dropped to 30.5psi and maintained that boost to redline. That mainly happened because the boost controller was not designed for that level of boost.
A lot of people have the misbelief that because a motor is bridge ported automatically means higher rpm's. Unless you have the supported mods to do so it ain't going to happen. I've seen many bridgeported turbo motors do no better than streetports both power and rpm wise. It takes more than just porting to make a bridge port motor work successfully.