Non-Seq. Boost/fuel/mod Questions
 

First off, motor mods:
non-sequential
intakes
down-pipe
catback

It's tough, after the various threads I've read, I'm trying to get a clear answer as to what boost I should be running, and what fuel mods are necessary right now with my current setup. I know it's been discussed multiple times, but here's the thing.

I am running non-sequential @ 8 - 9 1/2psi via valve-type MBC right now, and it runs great with no fuel-cut.

However, If I try to boost 10psi, it will hit fuel-cut at the higher RPM's in 2nd, 3rd, etc. First gear never hits fuel-cut, though.

Now, based on what is considered to be known by all FD owners, you are not supposed to run more than 12psi on stock ECU, and I understand THAT much, duh, however, why am I hitting fuel-cut at only 10psi then? I don't WANT 12psi anyways, it's too risky IMO, I just want 10psi.

My first thoughts were to replace the fuel-pump and see what happens. Wouldn't be a bad idea anyways, considering I'll be needing a fuel-pump for my future mods anyways.

What at least makes sense in MY mind, and the mind of my shop owner friend, who's owned 5 FD's... with intake and exhaust alone, you increase the overal air-intake and exhaust flow so much that even 10psi is too much for the stock ECU without it leaning out and/or fuel-cut. Aparently this is what I am experiencing, so you could say I'm talking from personal experience at the moment.

So what I would like to go ahead and do regardless of the answer, is buy a Walboro 255lph fuel-pump.

What do you think?

dude, have you been drinking?

I was hoping more for positive input...not an insult. :/

It's just a question.

I'll make it simple.

"Why am I hitting fuel-cut at only 10psi on non-sequential with just intake and exhaust?"

i am no expert on fd's but maybe you are spiking. Plus i would go ahead with the fuel pump. not expensive and they do a great job.

Stock ECU *should* be fine for 10 psi even with a midpipe (if you port the wg). Wade L. compiled some wideband data from various cars on the stock ECU.

http://www.newwave.net/~flanham/wlan.../3modrule.html

You want to verify this with a wideband though -don't guess on replacing parts (ie fuel pump), but make sure you have good plugs and a new(er) fuel filter.

Stock ECU wil cut fuel @ 10.7 psi in the upper revs (.7 psi is withith the margin of error on cheap boost guages)

Gotta love cheap boost gauges.

Fuel-filter I'll go ahead and replace.

Plugs: I have 2 sets ready, so I might as well do them as well. Does it make sense for it to only do this "hesitation" at 10psi according to my boost gauge but not 9 to 9 1/2 psi?

I'm confident in the accuracy of the gauge, because if my MBC is set too low, it boost 7psi, which is normal for non-seq, having bypassed some of the restrictor pills, etc, u know.

My friend whos FD is having all the boltons including Power FC ECU, is having Exactly your same problem and we are still trying to fix it.

Nice to know I'm not alone.

I'm talking to JacobCartmill on AIM right now and aparently I'm not hitting fuel-cut? What else could explain this "hesitation" I am getting?

It's not like "hitting a brick wall" or anything that extreme, it's more like nodding your head foward. The car loses boost, but will regain it, and continue to rev, usually to redline without hick-uping again.

I have it running 9psi right now as I've said, and it runs beautifully, but again, IF I were to turn it up to where I get 10psi in my 2nd, 3rd, etc gears, then it has done this "hesitation" at higher revs, usually 5.5k or around 6.5k.

Start with ignition (plugs, wires, coils, harness)

..get a wideband hooked up.

It was suggested to me to take it do be "dyno-tuned" to get a good look at my AFR's and see if maybe I'm pre-detonating.

I think I'll do that.

i said that hesitation could be pre-ignition OR it could be detonation. they arent the same thing, but they are both bad :) somebody correct me if i'm wrong here, but i think pre-ignition will give you more of a jerk when it happens.

if the car hesitates and keeps on pulling, its probably not fuel cut.

as i said before, you really should put the car on a dyno with a good wideband (almost all dyno's have a wideband hookup) before you blow a corner off of an apex seal. take it from somebody that has done it 5 times. :)

that is interesting.

i plan on testing this in the spring when i get an exhaust. hopefully the RB catback and the rx7store resonated midpipe. i've already got a downpipe...

but yeah, we have a a good mustang dyno here locally with a nice wideband setup and i plan on dynoing once with the stock cat/catback and once with the midpipe/RB catback...

Spark plugs, as Marshall suggested, are the likely culprit in this situation, after talking with a fellow avid RX7club member who's experienced the same thing, even on his completely different setup.

You are not hitting fuel-cut, sounds like a basic ignition problem to me. Even if it weren't, "upgrading" the fuel pump would do NOTHING.

As has been repeatedly proven over a span of 13 years, the stock ecu can support all bolt-ons at 10 psi. If everything is running correctly, your AFRs will still be at 10:1 or less from 4000rpm to redline with the stock ecu.

Replacing the plugs should most definitely be your first course of action....

Agreed. Fuel cut for me has always been like hitting a wall, not a slight hesitation

well yoshi, replace the plugs already... then report back

This man is an EXPERT at blowing/rebuilding engines.

I put all 9's in yesterday along with some Taylor Pro spark plug wires that were VERY thick, given to me by the previous owner, along with the car. He said they cost a pretty penny..

Immediately after, it seemed to be having this slight issue though where it'll drive and boost fine, but in traffic, lets say I move 2 feet in 1st gear then let off 1st gear to brake, the idle will drop pretty low, lob a little bit around maybe 400RPM, then catch itself within about 10 seconds, and be back at -15 vacuum and 700-800 idle.

Today I ran WOT on the highway a couple times and it was STILL giving me that "hesitation" on the way to redline in 2nd and 3rd, etc.

Again, this is only at 10, MAYBE 11psi... It just doesn't make sense.

I'm frustrated.

P.S. A more accurate way to describe this "hestitation" is, it will be revving, then the rev might drop back 100RPM and the boost will go down to lets say 9...then build back up to 10-11psi, and either continue till redline, or possibly even do it again before hitting redline.

sounds like preignition to me. i'd turn the boost back down.

Does the car make any funny sounds? When you hit fuel cut it almost sounds like the car is ripping a huge fart....sort of a "BLAAAPP" sound. I dunno man, sounds like you're trying to feel your way around in the dark without any kind of diagnostic tools at your aid.

Must have been pre-ignition.

Been talkin' to Jacob here for a while.

She was at least driveable last night.

Tonight I just had my friend take me to her to drive her home. She started up...lumpy idle @ rougly 400RPM... maybe -10 on vacuum...then stalled out and won't start back up now. I smell fuel.

Chipped apex seal(s) sounds about right.

Looks like I just lost a couple G's. $12,000 in loans on a car that doesn't even fucking run.

Hooray for me.

I'm just going to have to lose out on the $3k loan on it and just sell it for $9k non-running. $9k is the minimum to get the title back.

I hate my life right now.

did you do a compression test?

and good luck selling a blowed up TII for 9 grand...

It's not a T2 dude.

It's a '93 Touring FD.

lol.

^