So what's the deal with this, is my turbine wheel too small? I have a t3/t4 with an ar of .48 on the turbine and a .6 on the compressor. When VTEC hits it feels pretty bad and almost like it's reached its limit. Anyway, I"m running a JRSC fmu which is like a 5:1 but I've tapped it into the intake manifold so I'll get an extra 5 -10 psi of fuel pressure depending on my IC drop and it's running full rich. I'm just wondering why it feels so flat when VTEC comes on as well as why it sometimes stutters and sputters when giving it full throttle. I'm also running an bosch inline and my stock 310-345 (too many people have said different things) injectors and it's a 94 lude.

 

the .48 A/R turbine housing is too small. you need at least a .63 A/R housing. the .48 is causing backpressure... it cannot flow enough exhaust gas out. this is what's causing your sputtering at high rpm and inability to rev all the way to redline without resistance.

next, your regulator is too low. you need at least an 8:1 modifier for the Jackson Racing fuel regulator. 10:1 is preferred.

VTEC is also not conducive to turbocharging. when the VTEC lobes engage, they increase valve lift, giving you a slight pressure drop as more air enters the cylinders. it's only for a split second tho before the pressure equalizes throughout the system. the second problem with VTEC is when the lift increases, so does the valve overlap... that split second when all 4 valves are open to help evacuate exhaust gases in the combustion chamber by using intake air to push it out. in a boosted situation, increased overlap causes "flow through" by allowing boost pressure to escape out the exhaust valves during overlap.

you want to use adjustable cam gears to tune out this overlap, decreasing flowthrough and maintaining power at the VTEC crossover. another avenue is to replace your cams with turbo cams from Crower.

 

Well, I've changed the plugs and it feels a bit better when vtec hits but still, it's not as powerful. I was thinking that it could be the small turbine and housing but still, I should be getting power until redline, I mean it's still providing boost, but another theory that a guy had on honda-tech was that I may be running too rich, so this is contrary to what you are saying. He was running an 8:1 and he was super rich so he tried 6:1 and finally went to a 4:1 with an vafc and is now making 220 to the wheels, so I'm wondering if this is my problem too.
Either way, I"m still hunting for the main problem.

 

you're not running too rich, and take it from experience that the turbine housing is too small.

or you can keep hunting and pecking around the answer. i've already dealt with a .48A/R turbine housing on the H22A.

 

well cuz I'm wondering about the greddy kit for the 5th gen ludes and why they use such a small turbine wheel and housing...I believe it's the td-05 or something but I know that a guy in my city has it and he's running fine with such a small turbine.

 

I think you're running too rich. You lude injectors are 270cc/min right? Or are they still 240cc/min for your car?

If they're 270cc/min then drop those in. I think you're car is bogging down and running super rich. The turbine housing may be a bit too small, but leanning out your a/f mixture is an easy and fast fix to your problem. If you're running 310cc injectors at 5:1 in the FMU then tone down the injectors to 270cc or 240cc and don't boost over 6psi. I'd put money down on it that you're running like 8:1 in the A/F range. I know I'm running to rich at about 10:1. Unless you decide to scrap the turbo (which would be stupid) and go with lots of nitrous then you won't need an A/F ratio of 8:1.

Try leaning it out. Put in smaller injectors, lower the idle fuel pressure to about 36psi, and see what happens.

 

I was also going to say that with boost...VTEC should feel freaking incredible! You should notice it hit. Not bog down either. I know when I'm under boost and at 4800 when VTEC hits on my car...BAMMM!!! Its awesome! And that's running too rich for safety till I dyno it...think what it would be like if it was dead on at 12.5:1!!

 

the greddy kit uses a TD05/06 18g hybrid mitsubishi turbine.


but it's not the turbine size, it's the size of the housing and how much exhaust gas it's able to flow without causig back pressure or increasing spool time.


but of course i dont know shit about what i'm talking about.

 

stock usdm 4th gen h22 injectors are 310 cc, just fyi. and yes that .48 a/r is too small, the h22 needs a nice big turbine housing.