Tacos 4KTQ I0vt Swap: The Red Baron - buying parts again

[themagellan]

Have you tried adjusting the boost lower? If it is a "Fuel Cut" it would only happen at a certain CFM via CIS Plate. Work your way to see if the problem goes away, if it does and you pressure tested everything might be time to start trying to get the poor bastard some more fuel.

[Hank]

Yes, what he said.

[AngryTaco]

Well thats what I did. It will hold 13-14psi all the way till redline. Any more and I get this issue.

And I did find one boost leak in the mm hose. However it isnt nearly big enough to cause this issue. The ibtake held over 20psi eithout blowing anything

Please dont think I'm 2nd guessing anyone. I'm just looking at all possibilities and enjoy the discussion.

[scubadave]

maybe the ecu is pulling shenanigans?

[GTJeff]

The MAC11 also apparently has a dynamic fuel pump cut that takes other factors into account.

[40v4kq]

I know I've said this before, and I'll say it one last time in hopes someone with half a brain reads this.

If you think the ecu is cutting fuel via the fuel pump relay then just hard wire that SOB and the cut should go away. What you do after that for a more permanent fix is up to you.

[ringbearer]

That's way too easy Dan.

[scubadave]

I did it with mine. just remember to shut off the ignition while you get into a horrendus crash as it will keep running after the car dies and is engulfed in flames. no big deal.

[AngryTaco]

This isnt a fuel cut issue guys. I know what fuel cut feels like. It feels like a minor concussion followed by several 4 lettered words spewed out with a bunch of saliva all over the windshield along with my big greasy american cheesburger and fries being horrendously thrown about like an underpaid line cook tossing a ready to bake salad.

That being said however, I'm going to hook up a fuel pressure gauge and monitor fuel pressure at the inlet to see if pressure is dropping. The pump is relayed, just not straight relayed as Dave suggested.

On another note, PICTURES!!!!!















ALREADY PLAYING IN THE SNOW!!! The following are in Sun Valley, ID

[scubadave]

hehe I already said it wasn't fuel cut.

[40v4kq]

Is it possible that you are maxing out the CIS and getting lean misfire? I've heard that when you run high boost with CIS you have to change the control pressure and maybe something else so that you still get proper fuel metering throughout the range that the air metering plate travels. THE NATRIX explained it all in a thread over on MG, but its been years since I've read it. It ahd something to do with not being able to make the arm move further for more fuel so you up the pressure it sees at the high end of its travel arc.

[AngryTaco]

Yeah you have to shim the fuel distributor which raises control pressure. Ive shimmed it already, but Im going to add another shim and see the difference

[themagellan]

Something I feel a bit stupid for not mentioning, but may be a stupid question.

When I was having a "Fuel Cut" it was because my ECU line was busted from the motor. This in turn made the car think it was running 10psi but really more like 18 - Thus the timing was in hulk mold and when it was cold out it would give me the same hamburger fries and vicegrips through the windshield cut. Looking back on that it was obviously (DUH) the knock sensor telling me to go fuck myself.

That being said this was all on motronic and with a 20v - however my point here is it's very possible that maybe your knock sensor is working. A lot of ABF/9a 16v dudes would run a shim or spacer on the knock sensor.

Or maybe i'm completely off track and the knock sensor does nothing but retards timing gradually.

[AngryTaco]

When the knock sensor goes off, the timing is backed off by 2-degrees. If the timing is retarded more than 8-10 degrees, the ecm goes into "Low Octane" mode and references the maps for 87 octane. It was a fail-safe programmed into the ecm in case of a moron not understanding WHY high octane is needed, or if only low octane fuel was available (as in my case when leaving Sun Valley -- only thing available at a station was 85). Each minute that the ecm does not detect knock, it will add 1-degree of timing until it slips back into normal mode over a period of 8-10 minutes.

When the ecm detects enough knock to go into "low octane" mode, it will flash the check engine light and display a code when read.

I am not experiencing any of these above issues so I know I am not knocking.

[AngryTaco]

Also, I have finally settled on a direction in which to take the car.

After or during the transition to VEMS, most likely after, I have decided what to do with the 20vt.

Most people are gonna have a heart attack and quickly bug Marc for a better tune on their 20vt.

JE Pistons 10.5:1 compression bored .010 over
Rods
E85
Tubular exhaust manifold
Big Turbo T3/T4 or whatever I decide. Probably V-band
284/274 cam (or something similar) made to My specs with about 11-15 degrees overlap depending on the turbo choice
100mm crank internally balanced
35mm SS exhaust valves
Built head (even though it already is) etc

I'm going to find myself another 20vt short block and start the process. The question is whether to do it before or after the supercharged 408 stroker for the dodge

[pilihp2]

I'm totally down with this idea, but I think that 10.5:1 is gonna be waaaay too much for the 20v. Might even have issues running e85 with that. You sure won't ever be able to run 91. I wouldn't at least.
Detonation city.

I'd imagine the 20v would even be hard to do F/I and 10.5:1

[AngryTaco]

Theres a 20v in europe that has 10.5:1 compression with a cat cam making 500+ hp. Im going off of his build and adding my own changes. Ive considered the detonation problems and there a are way to cure it, eitger through clever machining, or a rock solid tune

[gtn116]

Also run W/M injection.

[AngryTaco]

Yeah for sure. I was considering running a water/propanol or even a water/hexanol blend, but im unsure what effect those would have on the metals. I know they would provide a higher octane/energy content for sure though

Edit: methanol has the higher octane rating. Forget the other 2 I mentioned

[pilihp2]

Maybe run direct port Meth injection and some pre turbo injection to keep the charge cooler. That might be of good effect. 10.5:1 is just so crazy high. I feel like you could drop compression by a point and just up the boost a bit more.

[AngryTaco]

I considered that, but the problem is the limits of a 20v head. Since a big cam will only do so much and max out your flow potential, you have to find other ways of extracting every bit of thermal energy available. Evem with 9.5:1 compression and say 30psi of boost, you are running into flow issues. 25psi wont cause flow issues, but now you need to bump up compression to extract more heat energy. The problem is detonation with that setup but that can be combatted with alcohol, water, and a good tune.

Those numbers are strictly arbitrary btw. It could be more or less

[pilihp2]

Well whatever you do, It's going to be so freaking cool.
I would definitely do at least the direct port meth. Jim had some detonation issues with his 20v, so I'd say it's a smart idea to do on a 20v.

[viridia]

Deleted because wrong.

[AngryTaco]

Hi vridia,

Ive seen what youve done and its pretty impressive. As for me, no I have not solved the hot start issue yet. When I shut the car off, I watched the fuel pressure drop from 55psi to 15psi immediately upon shut off. That was the pressure between the WUR (block control pressure reg). Its supposed to drop to 45psi over 10 minutes. Everything else is within spec. I stumbled across a thread in the porsche forums about this same issue and the thing to check is the oring in the control pressure regulator in the fuel distributor. Its the 17mm hex on the side of the fuel head. It contains shims, a spring, and a plunger. I suspect that internal oring has degraded or tore due to ethanol fuel or poor installation. What will happen is fuel escapes back into the fuel return line upon shutoff and creates the vapor lock issue due to low pressure. Im checking mine tonight and changing the oring

[AngryTaco]

Well picked up a good condition urS4 steering wheel for like $5 yesterday lol. Now I dont have to run the chewed up one anymore