Overboosting..!

[Godzuki]

Hi all.

I bought my rex from here knowing that it had some mods (downpipe, full exhaust, hks induction & hard pipes). I was told that it was now overboosting and needed a pfc. I took the car to rx-heaven, they said it was unlikely that it need a pfc and that a bad hose/pipe might be causing the overboost. They checked it over & found nothing wrong so decided that perhaps a pfc would cure the problem. It was fitted and then taken out for a test drive, everything fine now. Except it\'s not, it\'s still overboosting to at least 15 psi & sometimes higher.
Aside from the pfc the only other thing they did was to unblock the air pipe. The air pump is still connected and instead of it going to the cat, it had a bolt shoved in the end of the pipe and was cable tied. They said that was no good and took the bolt out, makes a loot of whooshy noises now but would it affect the running too?

Please advise... I seem to have a good engine in spite of its 56000 miles and I\'d like not to kill it.

Rob.

[sadgoth]

Have you had the PFC mapped, or is it running a stock base map?

I would suggest speaking to Carl (Hayward Rotary), Pip (WGT), Geoff (RE Worx) or Ross (Dragon) and try and get the car mapped properly for the mods you have, as the base map may not be up to the task.

[Carl]

Hi Rob,
Your car does need the pwer FC and also probably needs the exhaust looking at,it will be over boosting because of the exhaust being too free.
Even if you mod the exhaust the car still needs a mappable ECU,the power FC would be best for you car.
The info given to you by whoever that said that you need a power FC is quite right.
But,it is not just a case of putting the power FC on the car,it also needs a decent map in it.
So the upshot of all of this is that you need 2 things,an exhaust with a bit of back pressure,and a power FC with a map other than the base map.
If you have any questions,please do not hesitate to ask.
Regards
Carl

[sadgoth]

great minds and all that eh Carl?

[Carl]

Originally posted by sadgoth
great minds and all that eh Carl?

  LOL
Regards
Carl

[Steve Burnett]

What would fitting a boost controler do in this case?

[Ed_RX7]

A Boost controller would help but really wouldn\'t solve the problem.......a decent map for the mods he has.......i know Rob wants to leave the car as it is for now but not sure how long that will last!!!:D


Rob call me, might know someone who could help with the mapping if he has the time.......LOCAL TOO!!


Ed

[Steve Burnett]

Okay so the boost controller stops the car overboosting but why fit one if all it does is cover up a problem?
Or is it really a safety device to stop boost spiking in the event of it happening.
Think I\'ll start another thread cos I am very interested in this.

[Ed_RX7]

Steve, I believe its more a safety device ...but if you have one you will know that it alsows you to control what boost levels you want to run from the cockpit.

[Godzuki]

Ok... So you all think my overboosting is due to the exhaust? I thought the pfc controlled boost?

All I want to do is have the car run safely, I\'m not worried about extra power at all, I would have been happy with a standard car.
On the other hand it\'s frustrating that I can\'t floor it if I want to.

What is the correct thing to do with the air pipe? Block or leave open.

Rob.

[sadgoth]

the overboosting is due to the fact that you have some mods and the PFC hasn\'t been mapped for them. Once you have the right map for your setup it will be fine.

[Godzuki]

I don\'t want to leave the car as it is... It\'s just that when I got the pfc fitted, they quoted another £350 to map it, that seemed a bit steep so I slowly backed away smiling politely.

Rob.

[20B_boy]

Excessive boost will be due to the minimal back pressure in the exhaust system. Easiest/cheapest method of fixingit would be to put back pressure into the exhaust system - I imagine u could pick up a used decent cat and back box for not a lot.

If the exhaust is that free flowing then its the size of the stock wastegate and its operation thats the problem. Power FC mapping will smarten up its response but cant make it deal with overwhelming exhaust pressure if thats the problem.

[Carl]

Originally posted by 20B_boy
Excessive boost will be due to the minimal back pressure in the exhaust system. Easiest/cheapest method of fixingit would be to put back pressure into the exhaust system - I imagine u could pick up a used decent cat and back box for not a lot.

If the exhaust is that free flowing then its the size of the stock wastegate and its operation thats the problem. Power FC mapping will smarten up its response but cant make it deal with overwhelming exhaust pressure if thats the problem.

Hi Rich,
I think you meant to say a lack of exhaust back pressure in the latter part of your post?

Rob, if you just put the exhaust back to normal then that will solve most of your problems as Rich has quite rightly said.
But you may as well have a stock car then too.the power FC in combination with the right exhaust and map will make quite a bit more power.
Regards
Carl

[20B_boy]

Originally posted by Carl
Hi Rich,
I think you meant to say a lack of exhaust back pressure in the latter part of your post?

Rob, if you just put the exhaust back to normal then that will solve most of your problems as Rich has quite rightly said.
But you may as well have a stock car then too.the power FC in combination with the right exhaust and map will make quite a bit more power.
Regards
Carl

Ooops, yes overwhelming LACK OF exhaust pressure.

Thanks Carl.