• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

seeing some knock retard

blakgtp

blakgtp

New member
did a couple wot runs last night and i got up to 3.8 degrees of kr. should this concern me? current mods are 3.4 pulley, sd headers, 104 plugs, dhp pcm. should i up pulleys to a 3.5 or 3.6?
 


i have no wideband and it's a dhp pcm. also i live in bc, so it's limited for tuners for grand prixs here
 
i noticed when i went like 3/4 throttle on the highway while changing lanes today it went to 1.2degress. and then last night at wot it was 3.8 degrees. it's only at high rpms
 
also this was on a 70 degree day , clear skys. so in theory it could get worse in the winter right? i plan to eventually get a meth injection kit, or an intercooler if i find a deal, but until then, i guess i should up a pulley size?
 


Pull your Supercharger off, port it, throw it back on & see if anything changes. Pulley up is still a good choice for the winter anyway.
 
If you can port it yourself, the larger outlet will in a nutshell, lower psi #'s a tad, lower outlet temps, which in turn lowers KR from the build up heat it had prior. It's free minus the blower gasket if you already have a dremel or die grinder...takes a couple hours or so...just make sure you check out all the how-to's if you do it...it's pretty straight forward and easy.

Also, DHP's like to run kinda on the rich side...you have upgraded mounts or have the dog bones flipped or running a 180* T-Stat? Do those too if you haven't...super cheap.

If you still have knock on the 3.4" after all of that...get an MPS system if you don't have one and swap the 3.6" on for the winter. It should be fine there.
 


If you port a supercharger and your boost goes down, something went very wrong.
OP I would run a 3.5, in my experience .1 bigger on the pulley was good for eliminating 3-4 degrees of KR.
What would really help is a full tune, but since you don't have access to that playing with other stuff is pretty much your only option.

Depending on how much boost you're seeing on the 3.4 it'll probably get worse come cold weather. For example if you're already seeing 11-12psi... Theres a goldie locks zone that the m90 likes to be in and weather brings it to both extremes with changes in season.
 
fry626 said:
If you port a supercharger and your boost goes down, something went very wrong.
Click to expand...

Really?

Care to explain?

Less restriction, same pulley size, same amount of air...since the Eaton M90 is a roots style blower and it creates boost by restriction...what happens when you remove that restriction? Oh...psi levels dip a little. Same reason you lose boost levels when you go from factory manifolds to headers. Flow.

But I'll be here all day.
 
Porting a supercharger correctly makes the blower more volumetrically efficient, not the engine. More air coming through the blower means more boost since the engine VE hasn't changed.
Headers make the engine more volumetrically efficient, that's why boost goes down.
 


I would like to port the blower, but im going to college 5 days a week and working, car is my dd. so i ill install the 18 tstat
if theres still knock ill pulley down
 
180* should help compared to the factory 195 unit...when I was scanning the car the temp of the motor actually sat anywhere from 10-20* above rated temp...when the silver N/A car I had was stock...it would get pretty toasty, think like 220-230* sitting. Even people that don't recommend the 160* don't realize the car really never gets under 170* once it is warmed up...cruising on the highway in the winter that is...think it was like single digit temps. My headter worked just fine too. Sitting in traffic on a hot day with the A/C it would still get close to 190*. 160's aren't as bad as they are cracked up to be but the 180* is the most practical choice.
 
You must log in or register to reply here.
Back
Top