mgtkr1

anyone give me a pointer? here goes, fuelling is spot on, drives lovely through the range and comes on boost strongly. however when under extreme load, too high a gear and letting the engine pull through to higher revs i get a loud backfire. did this at 15psi, since knocked it back to 12psi. its only when the ignition is under heavy load. new plugs, fuelling setup and timing is spot on. im guessing its eith dizzy,coil,leads or poss plug related. its not boost cut as it peaks/holds waay over 10psi without issue when not labouring the engine. cheers folks

also rev counter either wont work or works but not accurately.

essexRSTSouthend

Sounds normal to me ... this happen close to rev limit?

mgtkr1

no, id say its roughly when the turbo starts to wake up/ the beggining of the power curve. only does it from where the engine is out of the power in a higher gear. even then its only sometimes.

essexRSTSouthend

Ohh i see, Spark plugs been check?. Sounds like when i had worn spark plugs or even a faulty spark lead.

mgtkr1

i thought about the plugs, they were only changed 500mls ago though. ill check/set the gaps. dont suppose you know the gaps off hand do you? im running 12psi atm.

essexRSTSouthend

sadly not. i was using a set of ngk plugs and they wore down within a month running 12 to 15 psi of boost. So now i run denso iridium plugs and been fine since. The boost curve felt really flat and would miss fire hard on boost but no always.
Also had broken spark lead a year before this and only happend on boost.replaced the leads and sorted. Defiantly sounds like a spark issue mate.

mgtkr1

yeah, think ill go with iridium plugs next time mate. also check dizzy and get a grp a coil. sounds like a worthy item if replacing the oe stuff. cheers mate

essexRSTSouthend

There are cheaper plugs that can cope with 500 to 600bhp. Check out MSD Link above mate. But i just skipped that and got the denso ones for peace of mind.

GVK.

Depending on chip it could well have say a 15 psi boost cut limit, some chips for RST used to have boost limit removed completely.

If it was blowing spark out it would misfire and splutter rather than backfire IMO.

When I had my RSTs in the 90s, I used Bayjoo chips from Harvey at SCS, used to hold 16psi with -31 actuator. Used to run NGK BCR8ES in mine. Gaps were 25 thou from memory, whatever that is in mm

Rev counter could be the cluster itself, or wiring fault from the coil.

GVK.

With it being loaded up like that it will hit peak boost, if there is a boost limit in your chip and it's going over that, it will cut the spark, then backfire. You don't get the load in the lower gears.

It is chipped, isn't it? Not sure from this thread https://passionford.com/forum/genera...ers-today.html

Some good info from dazc on this thread https://passionford.com/forum/ford-e...ce-needed.html

blackbeautyzetec

Would think it would splutter on boost if it was the plug gaps. Always a first thing to do tho. What plugs you got?

Ford say 1mm for motorcraft plugs and ngk are 0.75 and I put mine to 0.6

mgtkr1

ive got the rec'd ngk. 20 notes for x4. i think iridium plugs would be a good investment. it happened again today. ive noticed a pattern here though, its only when you ask a lot of the ignition in 4th gear. with sensible use ie plenty of revs through the gears it doesnt happen. only when sat behind driving miss daisy and going for a lazy overtake (in 4th) im gonna investigate the plugs/gap em as appropiate in the morning. could overfuelling cause this. i know the on boost fuelling been correct has a detrimental effect off boost in terms of a/f.

luke19790_3

i'd get the car setup by someone who knows rs turbo's

GVK.

Do you have a boost gauge in the car? Have you looked at it and checked what's happening to the boost when you accelerate in 4th from low rpm? Sounds to me as though it's cutting the ignition as boost is going over it's limit preset in the chip (as said earlier, if it has one), as there is more load when you accelerate like this rather than accelerating using revs in lower gears.

When I've had issues with cars 'blowing spark out' it is usually in any gear/ hard acceleration it happens.

Also, thinking out of the box, is there a fault in the coil wiring causing this fault, and your failing rev counter?

We never used iridium plugs in the 90s....

mgtkr1

just looked in the ecu, and appears to be a std chip. still had the silver chip cover on but some sort of felt tip symbol. is that factory?

i think some ecu's cut bosst at around a bar, others less so. is that correct? also think my naff gauge is optimistic. it appears to be boost cut anyway, a real violent backfire.. sounds abouit right.

what chip would you reccomend, i hear bayjoo chips are about the best as they alter the timing, the rest only remove std boost limit. any tips would be handy. cheers fellas. the r/road guy i used has done many mfi turbo's over the years, just not recently. seems like a good egg tbh. i will take trip to oddkid at some stage though.

GVK.

0.6mm = 25 thou in old money

GVK.

As said earlier, I had Bayjoo chips in my 2 RSTs in the 90s, as Harvey at SCS is local.

A mate had a to quote Harvey "destruction techniques" (Detection Techniques became Superchips) chip in his RST in the 90s and kept blowing his up. Harvey used a Bayjoo chip on it and he never had anymore blow ups.

Does the soldering on the chip look factory? Must be threads on here with pics of standard chips?

https://passionford.com/forum/ford-e...s-chipped.html

https://passionford.com/forum/genera...urbo-chip.html

Your fault seemed familiar as when I had my first RST it would have an initial spike to 15psi then tail off to 9/10 psi, but if you gave the actuator more preload or used a bleed valve and raised the boost at all it would cut out with high load, after it was chipped and a -31 fitted it transformed the car.

mgtkr1

with an indicated 10-11psi it doesnt backfire. with 12-13psi it does only under load though (labouring in higher gears). so what you have said makes sense with what appears to be a std chip. ill go with a bayjoo chip then mate, thank for the input mate and to anyone else who had input. ill let you know how things go with a bayjoo chip/setup. cheers matt

nickscunny

iTrader: (1)

When mine was running I used to have an intermittant missfire around 4,500 - 5,000 revs I decided to investigate and still havent found the problem!