I am stuck. I put a Kenne Bell supercharger in a couple weeks ago, and after a few issues that I resolved, it runs great - only when the engine is totally warmed up.

When the engine is not completely warmed up, it is sputtering, bogging, and even coughing (not quite a backfire, but not even close to right).

Does anyone have any ideas?

Vacuum is solid 20 hg-in at idle, boost is solid 8.5 psi at WOT.
Idle is perfect, no problems there.
AF Ratio is good, 14.6 at idle, 11.5 at WOT
Plugs are Autolite HT0 gapped at .035

KB said to check the plugs.. With all other things going good, I am going to look there next, but don't plug problems usually get worse as the engine warms?

Has anyone tried the Brisk brand plugs in superchargers? Any luck?

 

Do you have a boost a pump? I was having this problem with my Saleen SC and Brenspeed told me it's common for this to happen with the BAP before the engine is warm. They recommended turning it down a little. Instead I reloaded my tune and cleaned out the throttle body and that resolved it for me.

 

Yeah, being a Kenne Bell supercharger, they include the Boost-a-Pump in the kit. Unlike Brenspeed, they don't run it wide open though, it is actuated off a vacuum switch. WOT when the engine is warm is great, and although I don't have my Fuel Pressure gauge yet, I have not had any issues with fuel.. The sputtering happens across the full RPM range though, so whether it's demanding a lot of fuel or just a trickle, it's happening. The Throttle Body was perfectly clean when I removed it and put it on.. not even a little gunk in there.

I let the engine cool for about 4 hours then got into it hard and it was pulling stronger than I had felt to date. KB is suggesting the plugs, and I wonder if one isn't broken, and making better contact once it warms and expands.. I might just drop the $140 for a set of Brisks, 2 heat ranges cooler than stock as is recommended for 450+ hp applications. The tuner at KB said they have had way better luck with the Brisks than with the Autolites. My wallet is empty at the moment though, this project wiped out my secret savings, and my wife is on to my spending spree, so I might just have to wait it out.

I reloaded the tune, just to be sure it wasn't an adaptive learning issue. I will wait and see the next time the engine is cold after a long rest.

 

i have beeen runing mine kbell setup for 16 months and she acts up on cold cold starts when i get into the boost but is fine when she warms up . i have a buddy with a pro charger and his allways acts up on cold starts when he gets into the boost before it warms up

 

time to start rebuilding the secret
account! lol

 

What plugs are you running? Autolites?

(I got another email from KB and they are strongly recommending the Brisk plugs instead of the autolites).

 

It is normal. I have had mine for a couple of years now and have had no ill effects of this happening. Just let it warm up and when the car drops into idle she will be good. Don't get in it until she is at optimal running temp. I have mine up in Alaska so I know about COOOOOOOld starts.

 

IIRC, KB recommends the gap to be .025, not .035...

 

I have a whipple and can hammer it from the get-go, so I'd say it's not normal.

 

I am running HTO's with the gap set to stock and no issues.

Best guess is a bad plug or Cops not seated.