Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Butterflies in or out?

Demon?

Terry?

Bnoon?

Aussie?

et al?

...et al...



Run 002 - IMRC not working
Run 003 - IMRC pinned open
Run 004 - IMRC working

Leave them in, let them work.

Without a way to add fuel or spark, leave them in. Otherwise, ditch 'em. Pinning the secondaries DOES NOT get you the same gains as removing them. I repeat... Pinning the secondaries DOES NOT get you the same results as removing them. Removing the secondaries entirely eliminates the secondary throttle rail that goes through all primary and secondary ports. This is where any high RPM gains would come from. Pinning them open is ONLY A TEST mod to figure out if you can live with the low RPM losses before actually taking them all the way out to get the high RPM gains. I can't tell you how many times I've had to type words to that effect.

BTW Ghost, you've got some fuel or spark issues there bud. That's one of the jumpiest dynos I've ever seen. Did they have trouble getting a signal or what?

Brad,

I can add fuel but not spark(yet). I have the SHM Mafterburner. It adjusts a/f at 400 rpm intervals. You can read the rest of the mods in the sig.

Do you have a how-to on drilling out the rods and filling the holes?

Can the ports of the LIM be drilled out to say 37mm with a drill press and polished by a machine shop? I realized that the UIM is much smaller, but that can also be taken care of in the future.

A local tuner is telling me that 02 readings are not an acurate way to tune, while HEGO sensors are. What is you take on that?

Has DemonSVT gutted his butterflies yet?

You should be fine with your MAFterburner, heck, all I have is the Pro-Flow MAF calibrator and I only had a very slight dip in my dyno curve. I could easily handled it with the Apexi, MAFterburner, Greddy, etc.

No "how to" exists that I know of. I plugged my holes with bolts that fit snugly into the holes and JB Welded them. The holes in between the runners I left open. I know it creates turbulence, but since this was just a test I didn't want to spend more time than needed. Heh, guess it's been a year now, time to finish up this "test".

O2's will get you close if they're accurate, but wide band is the way to go for best performance.

I don't remember if Demon has his or not. I think they're gone...

He's right. The O2's on your car are pretty worthless away from 0.45 volts, besides as a guide for approximation. A wideband O2 will be accurate at the 12.5:1 range you want to tune to. He's using the wrong terminology (the O2's on our cars are HEGOs), but he has the right idea.

You can build a UEGO a/f monitoring system for around $250-$300 if you're handy w/a soldering iron. Click HERE for the How-to.

This is the same thing as the $1000+ system that they use at the dyno places. And you can leave it on your car all the time to tune to you hearts content.

These GUYS also sell a kit to make the same UEGO setup. They were selling them pre-made but I think they are backlogged right now...

Yes mine are gone and I've been loving every second of it.

As Brad said PINNING them should show only losses. It's only a test NOT A DAMN MOD!!! WAKE UP PEOPLE! :p Especially when not done correctly to get the early timing & fuel ramp up.

Okay now that we've said that for the umpteenth time...

Also on A/F tuning. 1000rpm increments are the best. Except for where my power (timing & fuel) comes on (2500) and redline (7500). They are the only 2 places I use 500rpm increments. IIRC Kaiser has seen the same thing in his dyno testing.

I wouldn't bother boring the LIM out to 37mm when the DH UIM is around 30.5/31.8mm respectively & the 99-00 SVT head inlets are only ~34mm.

The late model 99 & 00 SVT's LIM is already:
Inlet: 33.5/34.5
Outlet: 32.5/34

I would port match everything and make sure they go back together aligned properly. There is machining & casting flash EVERYWHERE!

After extensive EH on my UIM it came back as:
Primary: 33mm
Secondary: 34.3mm

I still didn't need to open up the inlets of the LIM. (I did port match UIM to LIM)
However I did take the taper out of them to match the head ports. Which I opened a little as well. More truthfully I knocked a bunch of machining flash off that was pushed into the ports!

My original compared to my final numbers:

UIM
30.5mm/31.8mm ~ 33mm/34.3mm

LIM Inlet
33.5mm/34.7mm ~ same - UIM ported to match

LIM Outlet
32.5mm/34mm ~ 34.5mm/35mm

Head Inlet
34mm/34.5mm ~ 34.5mm/35mm (bigger valves anyone! Computer models show the valves are too small! Exhaust especially!!!)