Can someone explain this to me in detail a little bit.. Im wanting to start upgrading my bonneville; mainly want to add a little more boost by downsizing the pulley.. I have the exhaust done, intake, have rockers ready to install and run high octane fuel..

The PCM is tuned on it and the timing is advanced by about 35* at idle and around 15* at WOT.. Would this be considered KR?? Or is it pulling timing only if its negative *??

Another issue (and this is very concerning to me) is that what I "roll" into WOT and abruptly let off the gas, it pops.. Sometimes once, twice, three times. And it causes it to immediately drop to about -5*.. Is this false knock or is this detonation..

I also should say that running all the way thru 1st, 2nd, and 3rd my test says "no detonations". This does not apply to the previous statement about the "poping" obviously since im WOT thru all three gears..

If someone could explain this to me in a little detail I would be very grateful..

Thanks..

EDIT: Sorry, feel free to move this to the appropriate section if needed..

 

You have to change the timing depending on the RPMs and such, the goal (I believe) is to go knock-free at 18* on WOT. If you can do that, you can safely drop pulleys.

35 at idle is fine, but I would check the AFR there and maybe lean it out a little on idle and lower the timing to like 32*. Might be running richer than it needs to on idle, although it's not hurting anything.

It should have a valve to release the excess boost. Not 100% familiar with that part of the L67 set up.

Do you have your own tuning software? How are you monitoring KR? You should be able to have a KR monitor the degrees of knock, and you want to see 0 across the board.

 

I have not used the tuning software myself yet.. Its still on Milzy's tune.. I do have it and plan to start playing with it very soon. Which is why im asking this stuff..

ATM, i use the bafx module with the torque app.. Its kind of tricky because I can only monitor timing OR detonation, not both at the same time.. BUUUUUT, seeing as im gonna start with HPtuners soon ill finally be able to monitor correctly..

Thank you.

 

More details on the setup please. Current pulley size? What is 'exhaust' (catback only, headers, dp, etc)? What ratio rockers? Also are you running higher octane than pump fuel? The stock L67 is supposed to be run on premium, so if that's what you're currently running then it won't help reduce KR any further. Its different if you're on e85 or 100 unleaded or something.

I wouldn't worry about timing at all anywhere except WOT / heavy load. 15 degrees is a little low but isn't awful. Ideally I'd like to see it closer to 20. It's impossible to tell if it has KR by just looking at timing. It won't go negative at WOT from knock, it'll be reduced from the set point (ie the pcm commands 18*, sees knock, and pulls that down). You need to monitor the KR value to determine this. The PCM could just be tuned with low advance to allow some margin of error with people dropping to low of a pulley.

Popping on deceleration after a hard pull is common. My vette will occasionally let out a small fireball out of the exhaust when letting off after WOT.

Again, as you're out of WOT, I wouldnt worry about what the timing value reads. It's not going to be actual knock when you're off the gas.

I'm not sure what that means when you say 'test'. You should be able to pull up a gauge on your scan tool that shows the current KR value. That's what is important here.

I wouldn't be surprised if it was actually zero though across 1-3 gears, especially if you're on a stock pulley with mods and fairly low timing.

This is where it's beneficial to have your own tuner. It would be nice to throw a few more degrees of timing in it and see what happens. If you added timing, and KR pulled most of it back out, then a pulley drop probably wouldn't help (as you were already close to the limit and would have to pull a lot more timing to get it back to zero after a pulley drop). If it took another 4 or 5 degrees with no issue, then you could drop a pulley size and try the loop again.

 

Stock manifolds then 3" from there.. Plan on headers soon. Im still on the stock pulley.

1.8-1 for the rockers

100 unleaded..

I know what you mean by monitoring KR but what I got (my test) is just the torque app.. You go WOT and wait till the app says to let off the gas.. The only results you can get are "No detonations" and "detonations detected".. Ive always had no detonations..

I think im just gonna start with the tuner myself a little sooner than I planned..

I know i word things really strange sometimes..

 

Downpipe? I'm assuming that's replaced with 3" since you said everything from the manifolds back, but just want to make sure. Catback really has no impact on KR, especially at this level.

That's REALLY expensive gas for a stock pulley car. Is the plan to run 100 full time? You should be able to do a pretty significant pulley drop if you're going to run that full time. I'd imagine a 3.25" would be no issue, maybe even a 3.0". It definitely explains your 0 knock, especially on a stock pulley.

No offense, but I'd ditch that software. If it's really monitoring KR like that, it's completely useless. Certainly you've got nothing to fear with a stock pulley, but for someone with a modded car close to the edge, that could be catastrophic. I just imagine doing a run, it comes back and says 8 degrees of KR and then you get to go pick the pieces of pistons out of your catalytic converter.

 

Start with HPTuners and a proper way to monitor the car, then get it running 100%, then you can start seeing about dropping a pulley.

The tune is the most important part in a boosted setup.

 

I definitely agree the tune is important, but being that Milzy already tuned it, I'd hope all of the common 3800 things are fixed. With that and the few bolt ons he has, I wouldnt be afraid to slap a 3.25" on there as long as he continues to run 100 unleaded - especially if the pcm is only commanding 15 degrees at WOT.

 

Really? A 3.25 on a car without headers? I would have been comfortable seeing a 3.4 with a proper way to monitor KR just in case.

I mean, I know the race fuel is a nice touch, but some people have knock monsters and he has no way of truly knowing yet.

 

IMO 100 octane is a lot more than just a nice touch, that's 9 points over premium in many parts of the country and goes a long way towards reducing knock. Thats a pretty serious 'mod', similar to going e85, as long as he has no plans to go back to pump gas. Certainly headers would help too, but people have made more power on turbo setups with the stock manifolds. No doubt they would free up power as they're a real restriction at that point.


I guess my point is just that spending $100+ / fill up to only run a 3.4" seems crazy to me. Certainly if he has that kind of money to blow, he should be able to afford a simple scan tool to go along with the smaller pulley to verify the 3.25" is good to go, but with all of those mods and the conservative timing it should be good to go regardless how knock prone the engine is.