95Juan

Hola, fellow rennlisters. this is my first post, i own a 1986 951, i dont have many mods, but enough to burn most cars in my area. i'm running- Guru chips, Lindsey Boost Enhancer, Kokeln K&N filter/adapter, 3.0-Bar FPR (Bosch), and a full exhaust that consists of- 3-inch piping, Dynomax Bullet Muffler in place of Catalytic converter, Magnaflow 3-inch exhaust, and a plain tip. oh, and the wastegate dump pipe is now........dumped to the atmosphere, . my question is- is there any reason that i should have a lot of "popping" when i let off the throttle? is it just that i'm running really rich and there's lots of excess gas? before i got rid of the catalytic converter, when i would shift at WOT, i had like a little cloud of dust coming out of the exhaust, now it's fire, which i admit is kind of damn cool, but the popping around town is almost annoying, is there any way to remedy this, or am i just going to have to keep tripping car alarms when i pass by them?

Clowd

I have this problem, and I have almost exactly the same mods as you.. however, I don't think I shoot flames? If I do, that's really cool.

But having a non-smelly, non-fire breathing exhaust would be cool too, so if you figure out how to fix it, let me know.

Jeremy Himsel

The exhaust popping you get between shifts during light driving is very typical of Guru chips and a test-pipe. Your flames are a result of your AFM chips being mapped for a certain PSI (probably 18) and your WG is not holding the boost level so you're getting a bunch of extra fuel that is burning late in the exhaust.

95Juan

it's the stock wastegate, but the boost pressure is 15 psi, the wastegate opens once my stock boost gauge hits 2-Bar (1 bar in the real world), the wastegate seems to be holding well enough now that i got the wastegate dump because i used to drop off in higher rpm (5800-redline) to about 11-12 psi, and now i'm barely dropping at all. is there any way to lean out the mixture without going to standalone? i know on my last 944 (1984 n/a), i had a full exhaust, and it did almost the same thing (minus the flames) i was considering A'pexi SAFC-II for that one, but then it got crashed into (ford bronco, the bane of my existence), but i dont think that the SAFC-II is reccomended for most turbo cars because it goes off the TPS, not the AFM/MAF, so it wont account for boost. any suggestions other than 800 dollars on a lindsey MAF kit?

Jeremy Himsel

$300 on appropriately mapped Vitesse chips will resolve your issues provided you don’t have maintenance issues. I’ve installed several sets of Guru chips and they all did it. I’ve installed five sets of Vitesse chips with mods similar to yours and none of them popped.

DDP

Popping is normally from a lean mixture or if the timing is off.

95Juan

derek, it really doesnt smell like running lean, and i'm not down on power, and my mechanic (Frank's Automotive. Sac. CA) says it's rich. jeremy- where can i get Vitesse chips? i tried a google search, and i cant find them, i always hear about them, but i've never seen them. also, it probably sounds like a completely retarded question, but i'm new to forums/posting/replying, but how do i put that lower part on my replies that says things like my name and my cars?

Jeremy Himsel

www.vitesseracing.com

TRWright

Welcome to Rennlist!!

The Vitesse software is the best. You will be very pleased.

As for adding a signature, that is a 'members-only' privilage. If you are interested in becoming a member, check out this site:

https://rennlist.com/members.htm

Clowd

Hmm, looks like there's my problem then... guru chips + test pipe..

MAF question:
If I get the $1250 vitesse MAF, that means I have to get new $300 chips to go with it, right? What if I get the chips now, then save up some cash and buy the MAF later, can I get those chips recoded for a lot less $$$?

Jeremy Himsel

The chips are included with the MAF kit. The MAF chips are very different from the AFM chips. John may be able to work something out with you. Send him an e-mail.

Skunk Workz

Popping in the exhaust when letting off is lean...you might run rich everywhere else,but on let-off you are lean. When rich it's more like a dull "boff"-sounding noise. That is,unless you run with anti-lag...rich,and way late ignition settings. Then it sounds almost like gunshots...that's why we say the rally cars here are "moose huntin'"...sounds like they're gunning down everything that could possibly move

daniel951

i am running the safc II and it works well and isn't that expensive
if you aren't running a cat isn't this one reason why the exhaust pops? This what i thought or if running rich?

KuHL 951

I'm going to be installing a Vitesse K26-8 AFM chip in the next 10 days so maybe I'll have some local info as to how well they do. Drop me a PM if interested. Vitesse is the only way to go if you are just doing a chip swap.