Half-Throttle Hesitation/Stuter @ ~3,000RPM
 

Here's my setup:

Turbonetics 62-1
850cc Pri 1600 Sec
HKS Twin Power Igniton
255 Walboro
Greddy intake man
Racing Beat Exhaust
kr2d fuel rail
Power FC w/ Commander
Greddy FMIC
Tial 90mm waste gate
HKS BOV

Yada yada...

Anyways...

If I go full throttle, no stutter...the car just goes...

If I go very little throttle....no stutter.

If I go like....HALF throttle, I get a really bad stutter/hesitation at about 3,000RPM..

Could it be the 850's being too much? It's been recommended to me go with 550 primaries for better street drivability....

Help?

Thanks y'all.

- Yoshi

Definitely sounds like it's the secondaries coming on. 550's could certainly help. It's difficult to complete tune out with 1600 secondaries.

I'm not nearly as mechanically-inclined as most members on here, nor my brother...

But for pulling an answer to my problem out of my butt, I'd say it has to do with either having such large primary injectors and/or, as you said, the transition between the primaries/secondaries.

As I've been continuing to read, it seems very common....

It's odd to read about people having this same problem with stock injectors too, though..

I mean....a STOCK FD doesn't have this issue....

But a basically tuned, NEAR stock FD does?

Hmm....

:/

Help?

This is the reason why a lot of fairly knowledgeable people on this forum strongly recommend avoiding the 850 primary's and just sticking with the 550's. It is my understanding, having been told by multiple builders & tuners that the 850's are just a pain to tune and not worth the effort. I have heard mixed stories though, some people say they have no issues with the 850's. You would have more than enough fuel with the 1600's and keeping the 550 primarys.

Notice that you say "basically" tuned. Find a professional tuner and then see if your still having issues. That or download Chuck Westbrooks notes ( join his yahoo group for $50.00) and learn how to do it your self.

I have the same stutter when my injectors kick in and out.