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3.4 Installed, still have KR and high boost-now what?

Liquifire

Liquifire

New member
I think I know the answer to this already but would appreciate any advice that I can get with this issue(s). I just got done installing my 3.4 MPS, 3800 PCM, AL104's. Now, I should have enough supporting mods to safely run the 3.4 set-up. I am getting as much as 12lbs of boost, and as high as 4* of knock at the top of second gear. What is my best bet to get rid of the knock? It runs awesome and feels good, but I am concerned with the knock. I am NOT going to put on headers, so please don't suggest that. Is it just all in the tune? I wanted to buy a 3.5 but they are all sold out right now and not available. I don't mind spending the time and money to get rid of the KR, but I will not be going beyond the 3.4 set up. I may go with roller rockers but I dont know how this will affect gas mileage and knock. I realize porting my LIM and SC would reduce my boost, but would it help with KR or not really? I never had any knock at all with my 3.8 but I did have boost on the top end of 7-9psi. With the 3.4 and the raised shift points I am now @ 12lbs.It is only 35 degrees here and I hate to see what it will be in the summer. When is the best time to tune a car? Is it when the worst case scenario presents itself? Warm weather or cold, does it matter?If there are any more questions that I can answer please let me know. My upgrades should be in my sig. Any real advice is welcome. Thanks again people....
 


the best way to get rid of that knock is to get a better tune. youre almost certainly going past your threshold limits and that KR is kind of false, but true at the same time. if you do not have any access to a tune then youre going to have to jump on the rocker train for a little more flow in your motor. ported blower/LIM/TB might help, but not as much as you would want it to. if you have 4* now, when its 0* outside youll have much more. when its hot you wont see as much knock because you wont be running as much timing.

if you dont want to do any of this then get a happy knob or a tune and run low timing.
 
what type of gains power wise would I see with 1.8 RR's...I should be able to run these with stock springs and retainers, right? I will find someone who tunes if that is what it takes, I will have to go to Iowa or Illinois I guess....
 
with rockers you MIGHT gain another 10-15 whp maybe and you could run them with stock springs.

your best bet is a tune. you car should run great after you get a good one, but until then i would suggest pulleying up so you dont knock a lot in the winter. i was seeing upwards of 14-15 psi on my 3.4 last winter which is way too much.
 
I just wont get on it until I can get a different pulley. I got a stock size to fit the MPS and the 3.4 but they didn't have a 3.5 available now. You think a 3.5 or 3.6 is my best bet until I can get it tuned?
 
it wouldnt hurt, but you could always just be nice to it until then. 4* on a 3.4 isnt that much knock, but over enough time it could cause problems if youre constantly in the throttle.
 


Liquifire said:
I just wont get on it until I can get a different pulley. I got a stock size to fit the MPS and the 3.4 but they didn't have a 3.5 available now. You think a 3.5 or 3.6 is my best bet until I can get it tuned?
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i would go with the 3.6 until your tuned... if your gonna have the 3.4 pully on hand, you miaswell bump up to a 3.6 for a winter pulley just to have. if its any reasurance, i have pretty much the same flow mods as you with a 3.6 and i dont have any knock, and i also have the gen 5 blower
 
I see 7psi MAX on my 3.4 setup. This is because it flows really good. Headers, rockers, ported m90. You really just need some flow mods.
 
Could unplug the BBV and see if you are getting the same knock first, it will limit the boost to 3-5psi.

Also, 4* isn't that bad either, how long have you been driving the car since you dropped to the 3.4 and put the pcm in? The fuel trims could be still learning themselves and you can be locking the LTFT's in rich/lean causing the car to lean out or dump fuel when in PE or throughout your upper rpm's.
 
FoSHO99 said:
Could unplug the BBV and see if you are getting the same knock first, it will limit the boost to 3-5psi.

Also, 4* isn't that bad either, how long have you been driving the car since you dropped to the 3.4 and put the pcm in? The fuel trims could be still learning themselves and you can be locking the LTFT's in rich/lean causing the car to lean out or dump fuel when in PE or throughout your upper rpm's.
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about 20 hrs since they were put on. about two hours drive time. So how do I drive it for now(I am assuming stay out of knock as much as possible) so that it does learn the proper trims and how long should it take to re-learn the trim's? I guess the 3800 pcm is not tuned to much to get rid of knock, or it is so individualized that I just need a custom tune, or everyone does...
 


not to kill your sale, but a 3.5 probably wont make enough of a difference to matter. its just cold outside and hes running more timing/boost than normal. in the spring/summer i bet the car doesnt knock if it had a good tune.
 
Bio248 said:
not to kill your sale, but a 3.5 probably wont make enough of a difference to matter. its just cold outside and hes running more timing/boost than normal. in the spring/summer i bet the car doesnt knock if it had a good tune.
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It probably doesnt help that I am running 200 more RPM's either at the top end. In first I only get just over 1* of knock and towards the top of second gear it starts getting bad. I will just take it easy most of the time until I get a custom tune.(Fosho or FastKatt maybe) Don't know for sure as I have talked to neither of them, but it seems the best logical thing to do. So is it best to tune it in the winter, summer, spring, fall or does it not matter at all?
 


if you do a conservative enough tune you shouldnt have to worry about weather, just pulley up a little bit in the winter.
 
Yeah that sounds about right. I mean colder air is more dense so u would see more kr in the winter. From what I've heard 4* aint bad. I'm not even sure what I have for kr
 
so how big of a difference are we talking in PSI? If I run a 3.4 in the summer at 80-90* should I be back to a stocker when it is 0* or would a 3.6 be a good bet?
 
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