My expo with just a 928 powerdyne aftercooled and water/meth/nitro 2gals of 100LL/110 ethyl to 20gals of 91octane and 1 5/8 shorty headers stock y pipe with hollowed out pre cats no down stream cats welded in straghit pipe and a flowmaster 3in cat back force II. I notced when i was washing the truck that there was burnt plastic on my tail pipe. I ran it for just a few mts enough to boost to kick in the meth. after stoping and shuting the truck off i could here the water sizzling on the tail pipe when throwing it on there.I thought this was unusual every other vehicle ive had the egt didnt get hot enough to burn the plastic strips the factory runs on the bottom for looks body skirt i guess its called. I have a 2 1/2 to 2 1/2 X-pipe i was thinking of having a muffler shop weld the x pipe in then have them run 2 3in. pipes with 2 chamber flows or somthing load but smoth not restrictve in the least. Oh i have a custom tune not to sure if i have to take it in for another tune after this??


Does any one think using a 3in direct fit flowmaster super 44 series muffler or a hooker aerochamber with a 3in. inlet and two 2 1/2 in. outlets and turn downs would help with lower egt's and flow?? would fumes still get in the cab if i have turn downs?? I just want less restriction and lower egts Ill go dual if i have to but will this help at all

P.S. after i remove this 5 month old clamp in flowmaster kit ill let it go for $125 and you pick up shipping i paid $400 if any one wants it

 

I ve figured out what Im doing now. The muffler guy in town told me he can bend me 2 1/2 to 3 1/2 cross over from the Y and I using a magnaflow race stright thur muffler 3 1/2in 3 1/2 out and he will bend me the 3 1/2 pipe back to the tail pipe. this should loosen up some of that bad back psi.

 

why not get a borla or aero chamber

 

egts are due to lean afr#'s .i'd be wiling to bet

 

Ive already gone over and over this with my tunner and of course he says its not his tune. Its runs pig rich in half moon bay, ca at like 50ft above sea but pulls hard as hell down there. The wide band shows no higher then 14.7 and will sweep depeding on full throttle or decelaration as low as 10 at warm up and when its real hot out and i get on it real hard it will hit 20 when leting all the way off the pedal untill i hit the pedal agin or slow down enough to drop into a lower gear. do you think the high alt. here in elko,Nv 5500 above sea level has a major part in it. Reno where my tunner is ,is at a lower sea level then elko.

 

I'm not much of an expert, but I don't think 20 A/F with FI is good?

 

your absolutel right anything above 14.7 on a newer fi ENGINE IS VERY BAD. To be more exact When you get in the truck and start it up cold the afr will be at around 10 while warming up and within a minute or so will be 14.5 at ideal. Now when the truck is at opperating temp 185 to 190 it s at 14.5 to 14.7. Now you get in the truck hard full boost it will drop to 12 and 11 which is great. Now while in full boost you just immediately let off it all the way zero pedal as you start to decelerate the afr will hit 20 under no load untill you hit the next lower gear or hit the gas agin then it will drop back down to the 14'S. I think this is normal as it was on my stang. But my stang never tripped my narrow band factory 4 O2 sensors like my expo does. My tuner said it would be good to drive accross country but it runs rich in Ca what gives My tuner is Jay at IVM motorsports in sparks NV.

 

So you don't have any actual EGT #'s to prove they are too hot? You just found something burned in the back and assume the EGT's are too hot?

Your A/F should only be at or near 14.7 while CRUISING. If you are in boost or at WOT, you should NEVER be any higher than 11.5-12 MAX. Anything higher than that and you are on seriously borrowed time.

I've tuned FI cars for quite a few years and worked for several shops who built some of the fastest and quickest Supras in the world and we never allowed the A/F to go higher than 11.2-11.4 on the dyno. That equates to 11.5-11.8 or so on the street which is right where you want to be.

Your tuner is full of crap if he thinks that 20 is ok

 

no im no using a pyrometer i have goten off the hwy and thrown water on the tip of the exhaust tip and saw in fizzle. as far as in boost i should look closer at the afr but if it was going to go it whould have doon so a lonf=g time ago so it not that lean. I talked my tuner agin and all he said is he would adjust the baremetric tables so the Mill light stops going off. Im just thinking at this alt. this tail pipe is a little to hot not sure what up but im going to fix it with less restrictions thats for sure and where the crappy powerdyne stops the vortech will pick up

 

Heres my answer to crapy back psi. when i get the vortech with 10+ psi i dont think ill need a whole lot its a Magnaflow #14151 3 1/2 inlet and outlet center/ center going to have the tubes bent next week and installed good by super hot exhaust tip![IMG][/IMG][IMG][/IMG]

 

Hollowed out cats are a big NO-NO, rather cut them out instead. Think about it, you have these huge empty chambers for the exhuast gases to build up in in the higher rpm range and no where to go. Bad for the flow and that would be your backpressure issue. You're taking the chance of burning exhaust valves too with all that back psi!

 

I didnt know thats thanks for the info dude. I only have the pre cats hollowed out aand the down stream are pipe weled in. I left the pre cats because I go to CA about 5 times a year and the highway patrol there will some times use a miror to look under your ride for cats but what your telling me changes my mind. So do you think this will get ride of that back psi. Thanks for your help its the best responce yet that makes sense I will get with my welding buddy next weekend. Do you think I should still put this 3 1/2 magnaflow cat back on the truck. I would have never thought the hollowed pre cats would have caused this and now this explains the passngerside blow header gasket i knew it was back psi but i had to idea it was the the empty pre cats thaks a ton dude.