Just Couldnt Get The Power Down

[Granthem]

I still cant understand how some of the "stock" r33s etc get into the 13s down south!

None up here can do that, and my r34 with a cat back was only running 94mph. Which would need a crazy launch to even get close to a 13.

I dunno how you guys do it

[HKS-R33]

Hey guys, i scanned the dyno readouts so you could see how it makes power. The 260kw run was done on a 38 - 40 degree day, i think thats why its a little lower.

I really want to find out why my mph is so low. I was going to put some cams in but maybe i have some sort of other problem which i should fix first.

Any help would be appreciated.

Mike.

[R31Nismoid]

Dyno sheet doesnt mean anything dude, because we've told ya it wrong based on the very low MPH/ET you have for that power/setup

[2rismo]

The dyno sheet looks like the car has a reasonably broad power band for the turbo you've got on it but the mph doesn't show even 260kW. How's your clutch?

[HKS-R33]

Im running an exedy cushioned button. I havent had it slip on me yet.

[HKS-R33]

Dyno sheet doesnt mean anything dude, because we've told ya it wrong based on the very low MPH/ET you have for that power/setup

I know what your saying but the car feels very fast to drive. Alot faster than 220kw worth. I posted the dyno sheet to show the power curve.

The car would have to have major issues if its running a 35r with 18psi and only putting out 220atw.

Could it be cause the car maybe drops of boost through gears?

Mike

[2rismo]

I know what your saying but the car feels very fast to drive. Alot faster than 220kw worth. I posted the dyno sheet to show the power curve.

The car would have to have major issues if its running a 35r with 18psi and only putting out 220atw.

Could it be cause the car maybe drops of boost through gears?

Mike

If it drops off very badly then could explain some/most of the lack of mph. Give it a rev, son!

[Lithium]

For what its worth my car traps at ~112mph on street tires on ~14-15psi with a GT30R making 270rwkw on a hub dyno, BUT its not running a very nice power curve - internal wastegate slows the spool from 11psi to 14psi quite bad so reaches 11psi by 3400rpm, but then only 14psi by 6000rpm. Have an AVCR to go in, so will have to try again with same peak boost/power but fuller boost/power curve.

Edited February 7, 2008 by Lithium

[2rismo]

For what its worth my car traps at ~112mph on street tires on ~14-15psi with a GT30R making 270rwkw on a hub dyno, BUT its not running a very nice power curve - wastegate slows the spool from 11psi to 14psi quite bad so reaches 11psi by 3400rpm, but then only 14psi by 6000rpm. Have an AVCR to go in, so will have to try again with same peak boost/power but fuller boost/power curve.

Great example. Could also be a reason.

[HKS-R33]

The car doesn't feel like it drops off boost between changes, but when i had a screamer pipe on it, i could hear that the gate would be closed for the first instant of 3rd gear.

BTW, thanks for the help

Mike.

[R33GOD]

i think its your clutch also. i spoke to andrew from kudos and he told me he wouldnt run anything over 245rwk on the exedy cushioned button. maybe its slippin without you even realising it?

[HKS-R33]

i doubt it. i should be able to realise if its slipping. it puts the power down in every gear. im thinking its got more to do with it dropping a bit of boost going into 3rd gear.

I actually brought the clutch off andrew and he told me it would be fine for 270rwkw.

Will probably change cams and get a boost controller for it to see if i can bring the boost on a little earlier.

Mike.

[shanef]

Check out the following expertly produced dyno graph showing two cars each making 270kW.

Which car is quicker over the quarter mile?

p.s. fear my mspaint skills

it has to be car b! caus everyone knows a fast car is one with the greater area above the curve :sorcerer:

[Lithium]

The car doesn't feel like it drops off boost between changes, but when i had a screamer pipe on it, i could hear that the gate would be closed for the first instant of 3rd gear.

Not sure if you are referring to my example or not - but what I meant by mine is that the wastegate actually cracks open before I reach 1bar. It doesn't fully open, but opens enough to greatly reduce the rate that it builds the last 3 psi or so and makes 4000-6000rpm feel quite hollow after you have felt how the car goes from 6000-7000rpm. I have an internal wastegate however.

See boost curve (and this is done on the dyno in 4th gear, where it will build much more optimally than on the strip):

I'd love to know, if its not too much of a hijack - if the experienced racers here think I could gain a bit on the strip when I have the AVC-R in there and set up to hold ~1bar flat?

Edited February 10, 2008 by Lithium

[2rismo]

What boost controller are you using on that? Something like a Turbosmart eBoost2 will allow you to set a "gate pressure" which will stop the gate from creeping open before a specific manifold pressure. You can use this feature to bring boost on much earlier in the rev range and use play with this function and the sensitivity of the unit to control spiking caused by the less gradual rise in boost.

[HKS-R33]

What boost controller would be best for an external gate? Im looking at the eboost 2, hks evc V and the blitz sbc spec R.

Mike.

What boost controller are you using on that? Something like a Turbosmart eBoost2 will allow you to set a "gate pressure" which will stop the gate from creeping open before a specific manifold pressure. You can use this feature to bring boost on much earlier in the rev range and use play with this function and the sensitivity of the unit to control spiking caused by the less gradual rise in boost.

[2rismo]

I like the eBoost2 as do many top racers but every tuner will have their own ideas.

[Lithium]

What boost controller are you using on that? Something like a Turbosmart eBoost2 will allow you to set a "gate pressure" which will stop the gate from creeping open before a specific manifold pressure. You can use this feature to bring boost on much earlier in the rev range and use play with this function and the sensitivity of the unit to control spiking caused by the less gradual rise in boost.

I had a Turbosmart bleed valve in there for that run and for my 13.3 @ 112, but am installing an Apexi AVC-R soon. I can set the target manifold pressure for several different RPM zones as well as the "gain". Also can configure adjustment for dealing with spiking or boost dropping, and have gear specific adjustments to "gain" etc to have different effects or correction in different gears.

Powerful wee unit, if you are inclined to learn how to use it properly - unlike the majority who just set a target boost level and hope it works it out.

[R31Nismoid]

I just ran a bleed valve with my gate.

Ideally your gate spring should be as close to the boost you want, and then you dont need a EBC at all as the wastegate is doing it job correctly by regulating the boost off the spring.

If you have a 10psi spring, and run 20psi boost, your going to have it gate creeping in almost every gear

[Lithium]

I just ran a bleed valve with my gate.

Ideally your gate spring should be as close to the boost you want, and then you dont need a EBC at all as the wastegate is doing it job correctly by regulating the boost off the spring.

If you have a 10psi spring, and run 20psi boost, your going to have it gate creeping in almost every gear

However as mentioned earlier, I personally have an internal wastegate - the reason I had not bothered with any other kind of boost control is that I thought the gate should close enough to do its job. Apparently I was well wrong, Cubes runs a similar internal gate setup and gets similar - before it reaches its sprung pressure it creeps open and slows the rate it builds the last few psi quite severly.