Cosmo Kramer

Well my car is up and running and just tweaking out some final details. Currently I am running the factory cats, no air pump, 24 lb injectors, 8-1 FMU and factory EZF chip. On the last run yesterday, after getting the S/C belt nice and tight at full throttle it will go to 7 psi around 4500 rpm and hold until above 5000 it goes to 8 psi and I get detonation. I pulled over and attached the leads to retard the timing but it was still there. Would removing the cats and/or adding an X pipe increase the scavenging and lower the high rpm boost a bit and in turn make it more resistant to detonation?

Tampa 928s

Could you hear the pinging, I can't hear a thing with mine, I use a Data Logger to see what the A/F ratios are. I maybe wrong but without taking more timing out you are on the upper end on boost with out an inter-cooler or Meth inj.

Cosmo Kramer

I can hear the pinging and it only comes in over 5000 rpm and over 7 psi. Lower rpm and mid range is fine and reducing the timing using the jumper just reduced the power at part throttle, helped reduce the ping a bit at high rpm but not completely. My A/F gauge is showing rich even when it pings but I am not convinced on it's accuracy.

Maybe I can get a chip burned that reduces the timing at high rpm and high throttle openings. I put a check valve on the EZF as per my instructions to keep boost out of the vacuum sensor. Will the EZF back off the timing if it sees boost or no? I am worried as right now it is below freezing and in the summer it will be less resistant to detonation.

Kevin Michael

Ted, You will never be comfortable or safe for that matter till you install a good wideband 02 such as AEM. Then take off that cheap plastic bosch BOV, and replace with a greddy or better unit. You can actually dial in the boost, to an extent. Get an air-to- water IC set-up from Tim Murphy and carefully work in a good fuel tune, richer is better with these things. Look for no leaner than mid to low 12's on the wideband at full boost. Ideal is 11:7 or close. Are you noticing a big difference in power, or just a little?

Tampa 928s

Tim had taken out a lot of timing out where needed, so it would be shark tuning time. Your best bet is to contact him and get a set of chips, I do not have the option of an inter-cooler due to the summer heat in Florida and Shane's was a prototype. I will be adding methanol injection very soon and am running about 7 Lbs now and will go to 10 once the M-Inj is installed.
http://www.coolingmist.com/

Cosmo Kramer

HUGE increase in power, on cold pavement the tires are scratching for traction all the way to 70 mph in second gear on the auto. First gear at full throttle from a roll and can't even keep it straight!

I noticed Carl at 928 MS sells a boost limiter valve which bleeds off excessive boost at high rpm. I think I would rather run it at 5 - 6 psi considering I don't plan to intercool it. I was hoping that pulling the cats would lower the boost a bit maybe bring it down to max 6 - 7 psi.

I am going to pull some plugs and take a look at the condition, see if they are looking lean or not. A wideband would definitely be beneficial I am going to take a look into getting one.

Cosmo Kramer

So does Tim supply chips to the 85 - 86 cars on his stage 1 kits? If so, that would be beneficial.

Landseer

I'm speculating here and don't have engineering knowledge. Seems like factory cats would be restrictive and potentially dangerous due to heat. You are moving a lot of exhaust now.

Also, 85 cats had fire problems originally. Be safe. Hope the boost pros weigh in on this. Might be a non issue but check!

Tampa 928s

I would ask him but I assume he has the ability to burn two for you. Get a Wide-Band they are cheap and look for an used Lm-1 Data logger. I use this to record my runs and feel a lot better knowing what is actually happening. The chips work fine for me!

Tampa 928s

If you want to keep the cats and not use a x-pipe take a metal bar and gut them.

jorj7

Ted,

This sounds like good advice. As for removing the cat and increasing flow
through the exhaust, it may reduce the "boost", but it will increase the air
flow into the engine. This should lean out the mixture even more, so you'll
need to increase the fuel also. Getting the mixture right would require a
wideband O2 sensor and gauge. Logging will make it easier to see the RPM
and AFR.

Cosmo Kramer

Thanks for the info I have sent a PM to Tim. I wasn't aware that he adds chips to his 85 - 86 models on a stage 1 kit.

I am thinking of taking the factory pipe off, cutting the cats behind the H and mig welding 2 straight pipes in their place. Or gutting them could be fun too!

PorKen

I hollowed out a set of plugged cats. I could not get out the protective metal chainmail that surrounds the ceramic without making portholes with a cutoff wheel. The cat bodies are made of thick stainless steel, so it was easy to weld them close with some SS MIG wire (spot welds all 'round).

(Definately wear a mask, there is some nasty dust that comes out of there when you bust 'em.)

123quattro

Like George said, gutting the cats will lean the car out (and make more power). Definitely get a wide band on there before you blow it up. Audible knock is dangerous.

Cosmo Kramer

Can a wideband be added to the factory H pipe with cats, I notice by Ken`s pic that the factory O2 goes into the H.

To be honest I thought this system was only going to produce 5 - 6 psi and that is how I set it up. Up to that psi it works perfect. I am getting very close to intercooler territory and I don`t want to go there LOL!