Hi, im having a problem with my car. 1st and 2nd gear seem fine, but when it comes on boost in 3rd and 4th it seems to be holding back or cutting the boost.

Its a 90 mfi s2 engine, stage 2 turbo, cone filter, -31 actuator, stainless exhaust. The ecu is standard but the boost gauge seems to show that it goes to 11psi and then drops to 10psi, i thought that this might be the problem that the ecu or amal valve is cutting the boost back to a 'safe' 10psi ?

It has NGK (i forget the number) plugs in. when i first got it running i took the car out, didnt notice any problem with the boost but didnt drive it hard. ive since taken them out, regapped them to 0.8mm. (i think they were gapped at 1mm) is it possible its blowing the spark out ?

Or any other suggestions. Cheers.

 

If you're only running the standard chip it has a boost limit of 10psi.

You will only noticed it in the higher gears as the boost gets chance to build up fully.

Get yourself a chip (and a bigger intercooler). Cant really understand the car having -31 actuator on it if its not chipped.

 

If it was a boost limiter cutting in you would know about it, believe me!!! The amal valve doesn't cut the boost it controls the boost level, the boost cut, momentarily cuts the ignition, usually follwing with quite a spectacular back fire. NO disrespect but is your gauge a cheap one?

 

Probably as said above, it's pulling more boost in higher gears, turn it down a couple of psi.

 

i agree with that, you will certainly notice if you were hitting the boost limiter as its the most strangest feeling you wil have the first time around.

and it makes a huge bang aswell. bit annoying when your racing about and your lead reduces massively cause you have hit the limiter!!

 

Cheers for the replies, to answer a couple of questions.......the engine is in an xr2, i have a front mounted 4wd cosworth intercooler. The reason it has the stage 2 turbo, -31 etc is that its built with the intention to up the power from standard so i thought id do it right first time.

I didnt know that when you hit the boost limiter it cut hard so that kinda rules that out as it holds back but not majorly. The boost gauge i suppose is a cheapy, the day i got it on the road i needed one asap and theres no decent place to get that kind of thing up here so i had the choice of a Tim one or Splitfire so i got the splitfire one.

Ive only had the car on the road a week and ive only really taken it out to see if there were any issues before i got it booked in to be set up. Ive read people saying set these NGK plugs to 0.6mm, 0.8mm and 1mm anyone know which is right ?

 

When you hit the boost limiter it does cut hard, as said. just try turning the boost down a little.

After having my s1 chipped... i was running 14psi but when i had certain electrics on, lights, rear screen etc... i could only run 11psi before it kind of hit a flat spot and wouldnt rev any higher but if i turned the boost down so it was at 11psi to start with it was ok. I knew it wernt the boost limit cos it was chipped and i'd been running higher previously.

I took it Well Lane and they changed the plugs, they put champion c59c in. It solved the problem. and i could run higher boost.

Could be the same?!....

 

Ideally mate get a set upif you can afford it, the MFI's are very temermental, ive just got mine running as it should but im going EFI just because im fed up with mechanical injection.