Backfiring, Through carb and exhaust
Turbo Mini Forums

Well iv got my turbo mini up and running, but im having a few running problems.

Its a standard metro turbo with the combustion chambers opened out giving me a compression ratio of 8:1, at the moment im just running standard boost of 3psi using a metro T3. Im also using the standard metro turbo carb with the standard BDD needle. And im using megajolt currently iv got the standard metro turbo map installed.

When im driving along at a constant rev for a while weather it be off boost or on boost i get backfiring through the carb, but this happens alot more when on boost. If i rev hard i dont get this problem it only appears to happen when staying at constant revs for a period of time.

As i get the backfiring through the carb but boost gauge flicks about to + boost even when im off boost.

Then when i let off the throttle i get backfiring through the exhasut.

Anyone got any ideas what my problem could be as im basictally running as a standard metro turbo would be but just with lower compression so i cant work out why it is running soo bad. Iv even brought a completely re-furbished carb but that didnt change the problem atall.

im gonna give it a stab in the dark and say its poping into the plenum because its lean. Im also gonna say check the timing and are the valve learences large enough?
That was on my na clubby but basicaly a good tune and it went great

Yes i moved to the darkside

Instagram @jdm_brett

this happened on a friends n/a engine. cos the timing was out and was running lean so brett could be right on both or at least one thing

tom you have pm

tom you have pm

tom you have pm

3 times by the look of it stupid computer! haha

Lol cheers guys pm'd you back.

Well im running megajolt using a standard turbo map, iv stuck the timing light on it, and if anything it is about 5* retarded, ill have another play with the timing and see if i can get that any better.

Fueling wise, when i took the plugs out they were a brown/black colour so as i would normally expect from a mini...

Yes i presume its backfiring into the plenum.

Lol cheers guys pm'd you back.

Well im running megajolt using a standard turbo map, iv stuck the timing light on it, and if anything it is about 5* retarded, ill have another play with the timing and see if i can get that any better.

Fueling wise, when i took the plugs out they were a brown/black colour so as i would normally expect from a mini...

Yes i presume its backfiring into the plenum.

Lol cheers guys pm'd you back.

Well im running megajolt using a standard turbo map, iv stuck the timing light on it, and if anything it is about 5* retarded, ill have another play with the timing and see if i can get that any better.

Fueling wise, when i took the plugs out they were a brown/black colour so as i would normally expect from a mini...

Yes i presume its backfiring into the plenum.

looks like mines doing the same lol, damn computer.

lol , from experience, lean makes it pop into the carb at part throttle and retarded will pop into the exhaust on overrun

edit, hang on already answered haha

Edited by Brett on 7th Jul, 2010.

Yes i moved to the darkside

Instagram @jdm_brett

Fair enought ill try ritchening it up and see if that helps.

I mainly get the backfiring though the carb when trying to drive round town in 4th, but in second its always fine, and on the odd occasion it will backfire through the carb in 3rd.

But the problem occurs when at slow speed in a high gear and accelerating (doesnt have to be hard acceleration)

Edited by tomf on 7th Jul, 2010.

Yes i moved to the darkside

Instagram @jdm_brett

Is the part-throttle lean off pipe connected and in good order or blocked?

In the 13's at last!.. Just

No unfortuanately i dont have wideband fitted.

Ill try ritchening it up a bit, when fitting the carb needle was i supposed to set it at a certain height? as i literlly put it in possition and tightened up the screw that holds it in place.

Im not sure what pipe the part lean off pipe is, but im guessing its the one between the carb and inlet manifold? if yes then that was a new pipe a couple of months ago. If its the take off slightly further back from that then i was told to block that one off, which i have done.

Ah, so you have the inlet connected to the ptlo pipe on the carb?

You need to either block both or connect it to the one further back.

In the 13's at last!.. Just

Iv just taken these pics of how its connected up:

Iv got the hoses connected up as (going from the plenum forward)

Fuel pressure regulator
Fuel pressure regulator
Blocked
Inlet manifold

Right, so it's no off the inlet at all. Lol

In the 13's at last!.. Just

Oh sorry my mistake i mean its off the carb at the inlet side.

Does the picture appear to have the pipes connected up correctly?

Yup, looks good to me.

Some have had different experiences, but I found that blocking off the lean off pipe was the only way to get the mixture stable.

Could be worth a go.

In the 13's at last!.. Just

Well ill give anything a go at the moment lol.

Also i forgot to add when starting the engine up from cold i get the carb backfiring alot more for the first minute or two.

It does sound lean.

In the 13's at last!.. Just

It could be lean, it could be timing, could be an ignition/spark or it could be a valvetrain issue.

Either way, it would be very foolish loading the car with boost if its lean, as you will melt something.

Get someone who can do some proper diagnosis before you do cause damage.

Edited by stevieturbo on 7th Jul, 2010.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will