we started tuning my car yesterday and seem to be hitting a wall at around 6000rpm. The cars power just drops off massively as if its running out of puff. The thing is, we are using a GT4094R so that cannot possibly be the case.

Are these intake manifolds restrictive? i hadnt figured that they would have been....certainly not before about 500whp?

The motor is a forged/sleeved 84mm block, stock sized head with uprated valvesprings/retainer, stock GSR cams. S300 ecu. Is the IAB setup killing it?

Can anyone help me out before i go spending money on something that may not fix the problem?

Thanks!

 

anyone got any views? we need to car to be making 650-700whp and this may be the thing thats preventing it as we arent seeing over 400 yet.

 

Why would you run a stock manifold like that, when trying to reach those power levels? That manifold is restrictive on all motor builds around 200whp unless a significant amount of work is done to make them flow better. It's always less money to purchase a single stage plenum like the OEM ITR style.

 

thats all i need to know dude.

To be honest when i was building the engine i looked at it and on face value it looked pretty good. However i didnt realise at the time about the 2nd set of throttle butterflys.

Would a stock ITR one provide enough flow? or should i just get a victor X and be done with it?

 

I would think that a stock ITR would do but I don't think you could go wrong with the Victor x at that power level.

 

thanks, thats great info. Much appreciated.

 

Hi mate

It was ages ago I read your build thread so can’t remember, did you have work done on the head such as port and polish? Also what springs and retainers you running?
I would look at future proofing the build, Victor X will certainly flow, also look at throttle body too, no point having a 42 up front if you can’t flow downstream.
The GSR or C4/C1 inlet with duel length runners are very restrictive, put one side by side with a the ITR of SK2 C1/4 equivalent and you’ll soon see.
I’ve used the I used GSR cams in my previous build, I’m now running 98 spec ITR’s and they make a big difference, again, it’s future proofing if you can drop a set of ITR’s in.


Eddie

 

Hi Eddie, the throttle body should be absolutely fine. Reason being is that on a turbo build the air is forced through to the chamber, whereas on an N/A build the size is more important. The exit of the turbo is 62mm, so if it matches that then there will be no restriction.

I just didnt realise that the GSR intakes were so crap!

 

Well i am running over 500whp with my oem gsr manifold . The butterfly valves are still in there too ! However i did open up the plenum to 65mm for an upgraded throttlebody . The car traps 137mph with a gt3076r turbo and weighs 2600 with me in it . At this point for me the turbo is starting to run out of steam @ 25 psi . So its safe to say the oem manifold can deliver . If your are looking for 700 whp then i would go to something else though .

 

thanks for your input, thats good to know. I guess for simplicities sake its best as you say to just get rid of it and get a better one anyway.

I guess your modifications did make some difference!

 

your running a gt4094 and stock intake manifold? wow. even at least a blox IM would help

 

its my first honda build, all my previous cars have been turboed from the outset so i didnt even think about it. My bad!!

It will be changed :D

 

I am shooting for 500 WHP on P72 Head.
I figured out the stock intake manifold would do it, to a flow point of vue.
to me though, the IAB, and all the webing in the manifold plenum need to be cut and ported smooth, as well as the throtle body flange bored to accomodate what ever TB will used.

car will be out and running soon, I if this post is still up to date, I'll post up the result.

Good luck with your build !