V1 EJ20G High Load/High RPM Cutout

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carfreak85
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V1 EJ20G High Load/High RPM Cutout

Post by carfreak85 » Wed Jul 18, 2018 10:41 pm

I'm in the process of resurrecting an EJ20G-powered 1987 RX coupe. As I catch up on the two previous owner's deferred maintenance, I've noticed that the car tends to cut out in high load, high(ish) rpm situations. It almost feels like a boost/fuel cut or a rev limiter, but I don't believe it's being caused by those safeguards. This happens after a few WOT pulls through the gears at my low boost setting (10 psi) and pretty quickly at stock boost (14 psi).

I've gone through the fuel system, new 255lph Walbro, new filter & soft lines (original, stock injectors though, waiting for my RobTune to upgrade). I've done the EJ coil-on-plug conversion in preparation for a RobTune, new NGK Iridium plugs (out-of-the box gaps), new green label MAF and I have a new, OEM o2 sensor that I'll be installing shortly.

The problem seemed to improve after the new fuel pump (can make more heat soaked pulls at 10 psi with a couple more pulls at 14 psi before it cuts out).

I spoke with SuberDave, who built the car, and he suggested dropping my plug gap down to .02x, since he had experienced spark blowout on a similar set up in the past.

What do you folks think? I don't want to install the RobTune ECU and 550 injectors until I've got this sorted out.
Last edited by carfreak85 on Fri Jul 20, 2018 3:58 pm, edited 1 time in total.
1975 Superstar Wagon
1984 GL-10 Turbo-Traction Wagon
1984 GL-10 Turbo-Traction Hardtop
1987 RX coupe
1987 RX Type RA
2002 WRX sedan

nosyt
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Re: V1 EJ20G High Load/High RPM Cutout

Post by nosyt » Thu Jul 19, 2018 1:56 pm

dropping gap is the quick and cheap way to check if you have a spark issue. if coil is getting weak it will easily blow out under boost and cause your issue. drop it down and see if condition improves then start pin pointing from there

mike-tracy
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Re: V1 EJ20G High Load/High RPM Cutout

Post by mike-tracy » Thu Jul 19, 2018 4:44 pm

I don't have a suggestion, just a comment that i was able to hit 17 psi with wasted spark coil pack on a td05 and VF23. Using Rob's ignition converter. Plugs were gapped in the low 30s
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

carfreak85
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Re: V1 EJ20G High Load/High RPM Cutout

Post by carfreak85 » Fri Jul 20, 2018 4:00 pm

Yeah, I think the stock gap out of the box is .04x or something like that. I also think I have STI coils, which may not be making great contact with the spark plugs, so also looking for some WRX coil packs to compare against.
1975 Superstar Wagon
1984 GL-10 Turbo-Traction Wagon
1984 GL-10 Turbo-Traction Hardtop
1987 RX coupe
1987 RX Type RA
2002 WRX sedan

nosyt
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Posts: 284
Joined: Wed Nov 19, 2008 6:31 am
Location: Otsego, Minnesota
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Re: V1 EJ20G High Load/High RPM Cutout

Post by nosyt » Fri Jul 20, 2018 6:53 pm

NGK PFR6G (Platinum Plugs) <-What EJ20G Shop manual recommends
Gap: .031" (0.8mm)
or

NGK BKR6E (V Power Plugs) <- Cheaper & Easier to Find.
Gap: .031" (0.8mm)

if you are anywhere near .04 I can almost guarantee that's your issue

mike-tracy
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Re: V1 EJ20G High Load/High RPM Cutout

Post by mike-tracy » Sat Jul 21, 2018 12:33 am

Ahh, the coil boots might be a problem. I've always heard that the ej25 coils boots were shorter to match the combustion chamber shape.
1992 Legacy SS 5mt, build in progress
Josh Colombo wrote:
Mon Jan 14, 2002 10:23 am
Wait....I'm confused now.

carfreak85
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Posts: 148
Joined: Fri Jan 16, 2004 12:04 am
Location: Bell-something, WA
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Re: V1 EJ20G High Load/High RPM Cutout

Post by carfreak85 » Mon Jul 23, 2018 5:37 pm

I spoke with SuberDave over the weekend and he said any plug gap over .030 would be too large, so I'll be pulling the plugs and regapping them this week.
1975 Superstar Wagon
1984 GL-10 Turbo-Traction Wagon
1984 GL-10 Turbo-Traction Hardtop
1987 RX coupe
1987 RX Type RA
2002 WRX sedan

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