Spocko

I was reading Corky Bell's Maximum boost for some help in defining my turbo problem, and I think it may be compressor surge but I am not sure.

I am running a Hondata Stage 4b, that was dyno tuned to stoich and retarted 4 degrees all around while in boost. Also I have a J&S Ultra safeguard V2 hooked up. Anyway here is my problem...

At part throttle, I can reach full boost levels(8.8 psi) no problem in first and second gear, but when I floor it to full boost, my car jerks/hesitates badly around 4000-5000 rpms(right about the time when it spools up to full boost) and then it continues fine all the way up to redline after about 5500- but it always happens and only happens at WOT. It feels like someone is cutting boost for a split second, then engaging, then cutting, etc in that range at WOT only- but it maintains full boost at all times, just loses and gains power in a rollercoaster fashion.

It is pissing me off big time- I wonder if it is surge related though because it doesn't happen at full boost in part throttle. Occationally the check engine light will pop on real quick when it hesitates, and then it immeadiately goes off again when the power resusmes, repeats, etc...

I do not think it is retardation from the J&S as I have it set all the way to minumum, and the fuel and ignition maps are decent, especially for low boost like this. It is really frustrating!

I have a T3(stage 2)/TO4 Super E .46 ceramic BB Turbonetics turbo with an A/R of 0.63, and a tial 40 mm WG. No boost controller right now to eliminate a possible problem source.(open atm. dump tube)

ANY help would be greatly appreciated!

Spocko_1701@hotmail.com

dustin

Sounds like it is not tuned right in the rpm range, running seriously lean...

AE86

I would double check your fuel maps.. Have someone tune it with a wide band meter and NOT at stoich. You want stoich only at low load levels! At WOT you do not want stoich. You should be at ~12.1 . To me it sounds like you are leaning out and that would explain the bucking. And you slowly accelerate and feed the throttle it's better right.

VaporTrail

Agreed, if it's tuned to stoich, you're running dangerously lean. You need at a minimum 12.5:1, but closer to 11.8:1 would be best for longevity. And double check that your Hondata unit's boost cut is set above the amount of boost your map sensor is seeing.

Spocko

Yeah I checked to make sure that the boost cut was above- but I am not sure if it is very lean or not- I used the maps from Doug at Hondata who dynotuned a program for the H22a with a similar T3T04 turbo up to 7 psi- and had it running stoich at full boost. So then I took those maps and to be safe added 5% more fuel to the entire boost table. Only thing I wonder is if by adding 2 degrees (advanvce) timing to the 2000-5000 rpm range is causing any problems.

Reason why I did this... well the timing maps are already set to 4 degress retard throughout the entire boost table from Doug at Hondata- so with my J&S Ultra Safeguard(which automatically retards 2 more degrees between 2000-5000- can't undue it either) I just added 2 degrees to the timing maps in that same range so the net timimg would still be 4 degrees retarded and not 6 degrees. Plus the fact that it seems to run fine after 5000-5500 at WOT makes me wonder why it doesn't buck the rest of the way to redline???

I will have to wait to do some datalogging in the spring when I get my car and new engine back, but I don't want to be doing boosting on a newly rebuilt JG motor and new RPS turbo clutch until the motor is fully broken in- so the wait will kill me to see what real boost feels like.