RB25 Missing

[Trent-KE30]

Hey guys i know this is a Toyota forum, but a mate has a 25 in a commodore, and it runs fine on 8psi, but when you try it on 14psi, it backfires and splutters when it hits boost over 10psi (4000rpm +), It's just a bog stock rb25 with a 'cooler. We have replaced spark plugs, coilpacks, new oxygen sensor. Now my question is do these have a igniter of some sort? I know nothing about these lol. Any help will be appreciated.

Thanks ! Trent

[riderzx10r]

whats your spark plug gap?

[Trent-KE30]

1.1mm I think.

[toymaz]

yes -igniter is bolted to the top/rear of the coil pack cover.

[riderzx10r]

try closing the gap up to 0.8mm the spark could be braking down under higher boost.

[Duk]

Hey guys i know this is a Toyota forum, but a mate has a 25 in a commodore, and it runs fine on 8psi, but when you try it on 14psi, it backfires and splutters when it hits boost over 10psi (4000rpm +), It's just a bog stock rb25 with a 'cooler. We have replaced spark plugs, coilpacks, new oxygen sensor. Now my question is do these have a igniter of some sort? I know nothing about these lol. Any help will be appreciated.

Thanks ! Trent

The ignition module is on top of the engine, at the back, between the camshaft covers, in the earlier engines. Later 1's (series 2 R33) had them built into the ECU. They either work or they don't work, there is no in between.

Coils can become a problem. Check for cracked bodies and fried boots that go over the spark plugs.

But it actually it sounds like it's reaching 'rich and retard' over boost protection and is based on AFM voltage output.
The maximum AFM voltage allowable some what changes with RPM. Well, that's how it worked on the RB20's.
A 'fuel cut' defender or better still, a decent interceptor will help, but the RB25 are rather prone to detonation and anything that tricks the computer into thinking that there is less load (lower AFM voltage) than there really is can be dangerous. If you are fudging the AFM voltage then make sure you have a means of reducing high load ignition timing.

[Trent-KE30]

Well just had a good look at the car and it has a link engine management system and no AFM, so i'am guessing it gets readings off the cam angle sensor and the link has a built in igniter?

[Trent-KE30]

Or probably uses a map style sensor?

[NME308]

Hey guys i know this is a Toyota forum, but a mate has a 25 in a commodore, and it runs fine on 8psi, but when you try it on 14psi, it backfires and splutters when it hits boost over 10psi (4000rpm +), It's just a bog stock rb25 with a 'cooler. We have replaced spark plugs, coilpacks, new oxygen sensor. Now my question is do these have a igniter of some sort? I know nothing about these lol. Any help will be appreciated.

Thanks ! Trent

Hi there Trent,

I had similar issues with an R32 of a mates a few years ago. We nailed it slowly over a month or so. This car had a pod filter and a 3inch cat back exhaust.

Some backyard bloke who professes to be a guru had butchered it up and convinced my mate it was going harder than any other '32 out there! He took me for a run and when it started to boost it would backfire and stutter and I had plenty of time to look over at the boost gauge and tacho etc while he was winding out 1st gear... It was actually registering almost as much boost as the stock '32 gauge reads just going like a stuck pig!

First I had him clean every electrical connector with WD and a toothbrush and remove and scrub every earth connector with sandpaper. Small improvement.

Second I removed the stock rubber intake elbow and replaced it with a mandrel bend. The factory rubber intake pipe goes soft over time and sucks itself together when large amounts of air are called for even with what seems like a free flowing pod filter. Much improved but still missing up top.

Thirdly I removed the stock coils and wired up an EL falcon coilpack in wasted spark configuration. Man that livened it up brilliantly! Most notably the boost was back down to more around the factory figure cos most of the fuel was now being burnt in the chamber instead of the exhaust...

Fourthly my brother came past when I happened to be flushing the crap (gutting ) out of the cat. He took a look at the huge rear cannon muffler and promptly grabbed a screwdriver and removed the giant restrictor out of the end! Well this is the point where I was jolly well praying this bloke could drive! We took my G-tech out and I managed to coach his take off down to a 14.1 second quarter with me on board and a badly slipping clutch. Clutch was slipping bad enough that I made him abort the last pass at the 3rd gear change cos I was afraid we would not make it back into town!

The original backyard butcher I referred to and a couple of his mates still to this day think I installed a larger turbo and screwed up the boost! All I did in reality was make sure everything was actually working properly so the car could actually use the free flowing intake and exhaust!!!

Cheers,
Jason

[Draven]

^ ^

as said, close the gap to 0.8mm. Very easy/cheap(free) thing to eliminate as a possibility, and quite possibly is the only problem.

my 2j has a similar issue if I don't re-gap the 1.1mm plugs

[88MKIII 1G-GTE]

Get a 1J.....



Sorry had to be said

[Trent-KE30]

Lol that's what i told him haha, its a bit of a sleeper so kinda cool lol , thanks alot draven and Jase!

[X kyle X]

My mate has a rb25 in his commo and had very similar issues and it was a AFM problem seeig as yours doesn't have one I would be inclined to try spark plug gaps and coilpacks

[Z2TT]

I'd probably say Coil packs too, most common problem I hear with RB's.