What does predetonation and Boost/Fuel cut feel/sound like?

[cis2711]

Here is my car: 1995 Ford Escort GT
1.8L-T GTX engine (NGK BKR7E plugs)
VJ-20 turbo
BP26 ecu
RX7 vaf
330cc(stock gtx) injectors
BP fuel rail w/ stock fpr
255lph walbro fuel pump
4 wire TPS
FMIC 2.5" plumbing
turbo smart dual port bov
turbo smart boost tee MBC (set to 13psi)
innovate LC1 wideband (needs calibration badly)


I have had my swap running for years and I daily drive it at 8-(10psi creeps) without a MBC on it. In the old days I wanted to run higher boost so I had a hallman pro mbc and set it to 15psi. I would get a weird full boost event back then and it appears I am still getting it now that I just installed a turbo smart boost tee mbc. Back in the day the wideband was working fine and afr's were prime under full boost, 10.5-11.5:1, idle was between 14 and 15.5:1, and cruise was 14.5-15:1. I removed the mbc the first time around because of the event and how it scared me...I didn't want to blow up my swap. Now I have an itch and I want to know exactly what is going on.

Here's the event:

Cruising up a hill, in 5th, usually under 50mph, floor the gas, boost builds to 15(in the old days), at some point under all this load the engine felt as if it hit a tree repeatedly and I swear it had blown up. I let off the gas a push the clutch in...engine idles fine.

However, lets say, 1st gear roll. I punch it..spools up violently fast and spins tires and roars up the street without event...
AND, in second at a roll. I punch it above a certain rpm...say 2000rpm, and it screams down the road at 15 psi without event..

Now, back then, if I were to punch it under 2,000rpm and the boost reaches 15psi in now time the event happens at low speeds in second gear, third gear, fourth, and fifth. It seemed as if all I had to do was cruise past 2,000 rpm in lower gears and all was well until 5th gear. It implied that too much load on the engine was the cause of the event.



With all that said, I have been creeping up on 15 psi all this week one click at a time. I'm at 13psi now. I haven't had the event happen until this morning. It barely happened but I distinctly remember what it felt like. This was in 5th gear up a hill and it spooled to 13psi and the engine felt like it shut off for a spilt second but sort of violently. I knew what it felt like so I tried again. No event. Again and again this morning I tried to reproduce the event and nothing happened. I'm very confused as to what this is. Until I recalibrate my LC-1 I won't know the current afr's.


So back to my original subject. Does anyone KNOW what boost cut/fuel cut feels like and what predetonation feels like?


- Cole

[cis2711]

I suppose I had better ask what spark blow out feels like too. Anyone have any experience with all of these?

[Boosted Escort]

spark blowout feels like you hit a brick wall. check your spark plug gap it may have changed. if the vaf maxes out it will probably cut fuel on gtx ecu. although with my gtr ecu and holset my b code vaf would Max out at about 5lbs. I went to a vaf out of a Turbo car. the vaf spring is heavier and won't slam the door all the way open as fast. I was getting way too much fuel with the b code. you guys with smaller Turbo can probably get away with the na vaf but they would still run better with a Turbo vaf.

[cis2711]

Im using a b code RX7 vaf I believe so that shouldn't be an issue? I'm not 100% about what I did years ago but I had it open and was watching voltage at idle and I think I may have adjusted that spring wheel inside the vaf to get a desired voltage at idle...may this have made the spring too loose on the door and possibly causing it to slam open and cut at high boost levels?

[Boosted Escort]

even the stock y gtx y code spring is heavier than the b code vaf. they are a coil looking spring.

[jay]

Spark blowout is often like hitting a rev limiter. The engine just breaks up, stutters, as sparks get randomly blown out. If one plug is slightly wider than the rest, if your spark leads are varying resistance with temp, these can keep the blowout thing from happening on all 4 at the same time.
Our stock coils start to run out of ideas at around 15psi, not enough oomph to bridge the std. gap. A Jacobs C4 coil is a cheap easy and highly effective upgrade. But whast you describe is boost cut. There is much more load on the engine on a wot top gear pull than there is when spinning tires in 1st.
Looking at your mods, I do not see anything that is adding fuel. You are pretty much at the top, maybe beyond the top, of the ecu map. a FM piggyback, a Reich IC, FPR mod, something, is in your future if you don't wanna blow up. Your setup is almost identical to what I had in my GTX when I rallied it, the exception being the HK$ piggyback for more fuel delivery. I never, ever hit boost cut with that setup at up to 17psi. If it were me, I'd turn the boost down til I got things sorted out. Hitting a brick wall with uncalibrated wideband and ignorance as to AFR's *should* be scaring the crap outta you.

Cuz pre-ignition and detonation doesn't feel like anything at all, right up till holes appear in the piston tops and rods ventilate the block. The only clue you can buy yourself is to, before you drive it again, pull the sparkplugs and inspect them real careful-like. Maybe even take a closeup piccie and post the results.

[cis2711]

I will take your advice and turn it down to 10psi. I believe that all this would be easier with standalone so once my tax return shows up I am going to order a PNP from Lex. Until then I'll get my wideband calibrated or replace the sensor, whichever fixes it first and monitor afr's again like I could years ago.

As for when I get a standalone, would 460cc injectors be big enough to run 15psi daily with the proper tuning from the MS2? Also, does it warrant getting a better fuel rail and aftermarket FPR?

[jay]

330 is enough to run 15 on a vj20, I did, with a nice big frontmount to add to the fun, for some number of years. Yeah sure I was priolly running more than recommended duty cycles but hey.. however, the instant you decide the vj20 is too small, you will need to upsize the injectors though.

[FE3-323]

i 2nd jay. your hitting boost cut.

a stock VJ20 even on a NA motor with a bp26 ecu is near impossible to blow up. so just turn the boost down a little bit. or spend some time & port out your wastegate(that will help boost creep significantly)

[atomicEGT]

you don't need 460s, a new rail, or an aftermarket FPR if you're using a VJ20. I used to run 20+ psi on 330s in my old GT (at like 110% duty, lol).

I'd swap VAFMs before going to a standalone, but I guess I'm just lazy.

[Boosted Escort]

go with a Y, A, R, or K U hybrid vaf and you can run it at 15lbs. only place I would run the b code vaf is on a na car. mazda used a heavier spring on their Turbo cars for a reason!

[atomicEGT]

Y or A for sure, I tried a U/K hybrid on my car and while it idled well, it was pretty awful under boost. worse than the B-code.

[cis2711]

I tried recalibrating the lc1 yesterday and it didn't work. I may have to recheck my wiring but I believe the wiring is sound. It was as if it didn't respond to the calibration ground switch I pressed. Normally it shuts the system off when you ground the calibration circuit but it stayed on the entire time while I tried.. Innovate makes an LC2 now...I may check into that if my wiring proves to be correct.

I will search around for a y or a code vaf. Does anyone here have one lying around they want to sell or give away ?

[atomicEGT]

Check the wiring for sure, I've had issues with grounding on LC1s before.

[cis2711]

tax return hit the checking account and I chose to get an MTX-L by innovate. MS2 is being built, rx8 injectors in the mail, and turbo is being rebuilt and hybrided with vj-17.