Going with slightly smaller pulley - need new chip burned?

**Z's Cobra** · 04-23-2003, 07:43 PM

I'm gonna post this here and the general tech area. I have the D1-SC and the motor is the stock cobra except for pro-m mass air meter, 42lb injectors, offroad exhuast, ati adjustable fmu and shorty headers. I have a mail order jms chip set-up for my current boost level. I'm running a 3.55" pulley and seeing 10lbs of boost. I'm going with a 3.35" pulley. I'm running a fairly safe tune. Do I need a new chip? Can I give it more fuel with the fmu and maybe retard the timing to avoid detonation? Thanks guys.

Brian

**Injected65** · 04-23-2003, 11:50 PM

Retarding the base timing and upping the fuel pressure with the fmu should work but as always it would be a good idea to get the car dyno'd with wideband to make sure that it will be safe after upping the boost.

Chris

**paluka21** · 04-24-2003, 07:28 AM

Originally posted by Z's Cobra
I'm gonna post this here and the general tech area. I have the D1-SC and the motor is the stock cobra except for pro-m mass air meter, 42lb injectors, offroad exhuast, ati adjustable fmu and shorty headers. I have a mail order jms chip set-up for my current boost level. I'm running a 3.55" pulley and seeing 10lbs of boost. I'm going with a 3.35" pulley. I'm running a fairly safe tune. Do I need a new chip? Can I give it more fuel with the fmu and maybe retard the timing to avoid detonation? Thanks guys.

Brian

Brian,
Are you positive your current blower pulley is a 3.55"? Reason I am saying this is because I was running a 3.80 on my D1SC and I saw 10#'s with this pulley and I have heads/cam. I installed a 3.55" pulley and am now seeing 13#'s by 6000rpm.
The car ran fine on 10#'s and was tuned on a dyno for this, however I upped the boost and blew a head gasket.
I am sure the JMS chip already has a total timing set into it, as well as fuel curves. I would call Chris Johnson and ask him what he thinks as he is the one who burned the chip for you.
If he says its ok to turn the fp up a little and back the timing off some, then so be it, however I wouldn't do anything until I talked to my tuner.

DAN

**WA2FAST** · 04-29-2003, 07:08 AM

When I asked this question to my tuner, he said that the car would most definately need to be re-tuned. He said, if you throw a lower boost pulley setup on it, then it won't be a problem, but if you up the boost... absolutely.

**Z's Cobra** · 04-29-2003, 11:08 PM

Well guys, despite your sound advice to have the car re-tuned and have the a/f ratio checked I went ahead and raced the car. It went 119.3 mph in the 1/4!! No blown head gaskets and no signs of detonation. I didn't change the timing and used only pump gas. I'm definitely going to get it tuned but I was amazed at how much power I gained. This is a car with stock heads cam and intake, full weight (about 3700lbs w/driver?) and all accessories running close to 120mph. I'm sure I'm just asking for trouble by not getting it re-tuned but I plan to put it on the dyno soon. My previous best trap was 114mph. It went from 10lbs of boost to about 15!!! And I only went one pulley size smaller. I really think that I was spinning that big blower to slow and it really liked it when I spun it faster. So I'm very happy, but I know I shouldn't press my good luck so we're gonna dyno it soon. Thanks again guys for the advice (even though I was stupid and didn't take it).:)

**Four eyed stang** · 04-29-2003, 11:21 PM

I would of raced it too!

Congrats!

**paluka21** · 04-30-2003, 07:05 AM

Great mph! What was the ET? Why dont you post a time slip of the run. When I went 119mph I dynoed around 460rwhp, so figure you should be around that, since 400 gave you 114mph.
BTW, with your 3.55 pulley I see 13psi @6000, I can imagine that the 3.35 pulley would see 15psi or more. What rpm do you see this 15psi at?

congrats

Dan

**Z's Cobra** · 04-30-2003, 06:59 PM

Four eyed, then I guess we both like living on the edge :D

Dan, my e.t. was only 12.2 on drag radials so I still need to learn how to drive it. It was really a beast on launch but I'm still running the stock t-5 so I really have to granny shift it. I'll get my 11.9 here real soon. I saw the 15 psi at about 5800 rpm but I haven't even watched the boost gauge at the track, I just saw that on the street. I'd post the timeslip but my scanner isn't working well (the wife screwed it up

I think she just messed up the software for it) but I'll see if I can get it working again and post it. I raced it last night and the air was much worse and it only went 117 trap at 12.7 (spun all the way thru 1st and 2nd on the drag radials). But I didn't get as much blow-by after installing a better breather on the oil fill cap. I have an incon one-way valve but with all the boost it was still blowing out the pcv before I put the better breather on. I'll keep you guys posted on her progress (the car's name is Rhonda btw) See ya

Brian

**paluka21** · 04-30-2003, 08:05 PM

Originally posted by Z's Cobra
Four eyed, then I guess we both like living on the edge :D

Dan, my e.t. was only 12.2 on drag radials so I still need to learn how to drive it. It was really a beast on launch but I'm still running the stock t-5 so I really have to granny shift it. I'll get my 11.9 here real soon. I saw the 15 psi at about 5800 rpm but I haven't even watched the boost gauge at the track, I just saw that on the street. I'd post the timeslip but my scanner isn't working well (the wife screwed it up I think she just messed up the software for it) but I'll see if I can get it working again and post it. I raced it last night and the air was much worse and it only went 117 trap at 12.7 (spun all the way thru 1st and 2nd on the drag radials). But I didn't get as much blow-by after installing a better breather on the oil fill cap. I have an incon one-way valve but with all the boost it was still blowing out the pcv before I put the better breather on. I'll keep you guys posted on her progress (the car's name is Rhonda btw) See ya

Brian

Great run, I can't say that I approve of your cars name man!

Why not name it something like butch!
Your times are very similar to mine when I was running about 10psi, but then again I have heads/cam as well. I went 2.0 60', 8.1 1/8th @90mph, and 12.3@119mph at best on bald 17" drag radials. I think the car had 120mph in it as well, but not w/ my granny shifting.
again, congrats and to be honest I would keep the car just as it is now, except throw it back on the dyno for another tune.. should be an 11 second car easily at about 121mph w/ some good tires, practice and tuned.

Dan

**Z's Cobra** · 04-30-2003, 09:01 PM

Dan, the only thing I may do to it hp wise is to port the lower intake, I've heard the stock cobra lower can use a lot of port matching to increase flow. Other than that, I have to concentrate on my cooling system. Because of my allergies I have to run the a/c all the time and the car gets too hot. I'm gonna try a 180 thermostat and some water-wetter and see if that helps. If not I may have to go with an aftermarket radiator.

If you threw your old pulley on we'd have some pretty cool racing action going on, red cobra's flying down the track side by side.

I'll try to attach a pic of Rhonda, never tried before so we'll see if it works.

**Four eyed stang** · 04-30-2003, 11:53 PM

I always liked those wheels! If only aftermarket made them in 4 lug.....

**Z's Cobra** · 05-01-2003, 08:06 AM

Thanks man, I'm a big fan of those rims too which is why I may have mine widened so I can put a bigger tire out back. No one makes them aftermarket in a 17X10 but there's a place in Michigan that charges like $180 to widen them and I might do that when my bank account gets back on the positive side.

**Four eyed stang** · 05-01-2003, 08:57 AM

I called a few local places about widening my 10-holes and was told I am crazy.
They said it would be unsafe and prohibitively expensive.
I knew I read an ad for a company that did it, but I couldn't remember where.

I just went with Weld's as I hadn't had a set yet and it is required that a Mustang owner have at least one set :)

**paluka21** · 05-01-2003, 09:03 AM

Nice looking ride, I really like the sleeper look too. So far all I have done to the outside of my car is polished Cobra R's. I had the stock rims on my car for a long time as well, however I ended up getting rid of them mainly because my center caps started peeling clear coat, and two of the rims were pretty badly curbed up from one time I slid off the road when the road was flooded over a small hill, which prevented me from seeing the water.
Yeah it would be a good run with my other pulley. I am going to be doing the same thing, having the lower cobra ported to the heads now that I have everything torn down.

good luck with everything
DAN

**Z's Cobra** · 05-08-2003, 10:33 PM

Update - have a dyno session scheduled for Saturday. I'll let you guys know how it goes. Anyone with any suggestions on what I should pay attention to at the dyno? I've been told to shoot for a 12:1 or 12.5:1 a/f ratio and to make sure my fuel guage continues to go up as the RPMs climb. The only adjustments I can make are to the adjustable fmu and the timing. I think I'm running like 12 degrees initial timing right now and the JMS chip brings the timing back in the upper RPMs. Any dyno and tuning experts chime in before Saturday with any good advice.