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About to take the plunge, looking for opinions.

Impala131

Impala131

New member
Alright, so my 99 GTP has a simple PVC intake and SSAC headers... like 90% of modded gps. So I fall into a very average demographic as far as modding goes. Now that I have the flow of the headers, naturally I'm looking at a pulley drop and a tune. I'm thinking that a 3800 performance (DHP) PCM with a 3.4" pulley is my best option. I want virtually zero knock (not just talking about KR). Do you think this would be a good combination?

I live in the Grand Rapids area and I'm open to having someone reputable tune the car. I'm also open to other mail-order tunes as well.

And although I'm not giving it serious consideration, I could also purchase HPT. The cost is high, but if I buy an aeroforce to check for KR as well as a boxed tune, I would probably have been better off just to buy a tuning suite to begin with.

Ideally, I'd just get a reputable tune in a box, not have to worry about KR, throw on a pulley, and go. I'm not concerned if I'm 10hp short of where I could be, I just want a safe tune to facilitate a pulley drop safely.
 


Do you mean toss a pulley on with the 3800 PCM or the stock PCM? And just curious, what specific programming changes make the former safer than running the latter? Fuel enrichment at WOT?
 
I think he means just put a slightly smaller pulley on, probably better with the tuned pcm and see if you have kr, you might not, then if you do you can start working to correct it.
 
Stock.

Canned pcms run pretty rich, add a degree of timing or two, and play with trans settings.

The trans settings are what people notice.

The fuel shouldnt matter much. Your intake affects your tune more than the pulley. However the pcm will see it needs a little fuel and end up adding it everywhere, even at wot.
 
Thank you for the insight, I thought it was pretty much a requirement to get some form of tune to run without KR on a smaller pulley. As I recall from my last thread, you said that I should run the smallest pulley I can on stock timing. So are you thinking I should drop to a 3.5, scan for KR, then drop to a 3.4 if safe?

And how effective is the boost bypass valve at negating boost during light throttle/cruising?
 


I get zero boost under light throttle and cruising, I only really get boost on like 1/2 or 2/3rds throttle or more, it's also dependent on how fast you're already going, like if I go to pass someone, it will downshift but I wont get much if any boost unless I want to and give it harder throttle. But if Im taking off and I put the same amount of throttle in, I'd probably see boost.
 
Ah, I see. Alright Fribo, I guess my real concerns are safe engine operation and not to kill my good gas mileage. I don't want to be one of those tards and just slap a 3.4 on and blast my engine. I'm just wondering how far I can get on just intake and headers. It seems "common knowledge" that 180* t-stat and colder plugs reduce KR, but I feel like they only help if you're riding the razors edge already with KR.
 
I would just try a 3.5 and if its kr free, leave it on. No point in spending more money for marginal power gain.

Boost and shift points is all to do with pulley size and again, mostly trans settings.
 
Alright matt, it seems like you understand what I'm trying to accomplish. When you say "marginal power gain", are you referring to a 3.5 vs a 3.4, or PCM vs stock PCM?
 
Both. Canned pcms can drown you in fuel and cost power.

.1 of a pulley size doesnt mean much. I can hardly tell the difference between .2 of a size. Might add 1-1.5 psi. .1 would be even less.
 


Alright, thanks. I've been tempted to go with a 3.4" because everyone has them (and blew their motor up with them) and they seem to be on sale everywhere. But I'll do my homework and play it safe for now.
 
The canned tune is recommended because generally these cars do get some kr with the drop to the 3.4 and running rich is better than blowing up the engine. The trans settings however are the real selling points/benefits with the canned tune.

However, every car is different and checking for kr with a scanguage will be the most effective. Maybe you find some kr, maybe you don't.

A custom tune though would be beneficial for even an un-modded car.
 
i had a 3.35 pulley sacc headers pvc fwi and tr6 plugs and i was on a stock tune for about 30,000 miles but it did have kr and sometimes it was alot of kr and u can tell LOL then i got a used zzp pcm off here for like 75 shipped guy had the shift points up to 6250 rpm car pulls all the way up there with 0kr most i have seen is like .2 and it downshifts at 40 mph into 1st which ripped the sh*t out of my motor mount under the oil pan also car has like 247,000 miles on it with stock engine if that says anything its all about scaning to keep the kr down and if u see kr dont just keep in it if u see them and hope the magic will take it away LOL only thing that will take is a piston i noticed the best gain from my setup was the headers then the pcm was mainly the trans settings also the ported blower seems to make it pull alot harder and smoother will find out soon on the intercooler and let you know still working on the install parts for that
 
00grandprixgtp said:
i had a 3.35 pulley sacc headers pvc fwi and tr6 plugs and i was on a stock tune for about 30,000 miles but it did have kr and sometimes it was alot of kr and u can tell LOL then i got a used zzp pcm off here for like 75 shipped guy had the shift points up to 6250 rpm car pulls all the way up there with 0kr most i have seen is like .2 and it downshifts at 40 mph into 1st which ripped the sh*t out of my motor mount under the oil pan also car has like 247,000 miles on it with stock engine if that says anything its all about scaning to keep the kr down and if u see kr dont just keep in it if u see them and hope the magic will take it away LOL only thing that will take is a piston i noticed the best gain from my setup was the headers then the pcm was mainly the trans settings also the ported blower seems to make it pull alot harder and smoother will find out soon on the intercooler and let you know still working on the install parts for that
Click to expand...

I appreciate the response, but holy sh!t dude, punctuation/sentence structure please!
 
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