What shall I boost to?

Guys,

I have a walbro, colder plugs, and FCD going in tomorrow. I also have a boost controller already fitted.

J-spec not UK.

I have a 2nd de-cat, and a straight though pipe with no muffler. The first cat is still there, and I want to keep it for noise reasons and to pass MOT.

I realise that I can't go "BPU" with the 1st cat still in place, but I do want to increase the boost using the controller.

Currently boosting at 0.95 ish as I haven't fitted the other parts yet.

Had some advice from a well respected member of this forum who I spoke to at Supra Pod that I could leave the first cat still in (I guess the first cat does the same job as a RR *grin*) and up the boost.

Can I have some opinions please, it is safe to gradually increase the boost up to 1.2 bar or so? More importantly, how will I know if it's causing problems?

Thanks!

James

I personally wouldn't go over 1 bar with the first cat in place due to high EGT's, get that first one out then you can run a max of 1.2 bar, I'd then get a piggy back ecu and get it mapped but that's just me though

if you de cat ityou will need some sort of muffler, trust me i know what a supra sounds like with straight pipes

I personally wouldn't go over 1 bar with the first cat in place due to high EGT's, get that first one out then you can run a max of 1.2 bar

Cheers, most people I have spoken to agree with this. I guess I have to bite the bullet and get it done - but it's sadly not as simple as that for me with my straight through system.

Am getting an EGT gauge fitted though so can still keep an eye of things in the meantime...

if you de cat ityou will need some sort of muffler, trust me i know what a supra sounds like with straight pipes

Yeah, it's a pain in the arse!

It's already really loud but in a nice way, I don't want to totally lose that with a muffler.

Also I am guessing that with my straight pipes there's nowhere to temporarily fit a cat for MOT *tears hair out*

Cheers

James

Did you do a run at pod??? if it's the one I think it is i'll put up this short vid clip of it, yours made this snap crackle pop that I'd never heard before prob got some pics of it too!

I did do a run, (not sure if you're talking to me or not!) however I wouldn't have been bouncing off the rev limiter like some!

There was a gunmetal one there that sounded like that though, maybe you're thinking of him.

I am Pxxx PKE... dunno if you have any pics!

yep its you

one sec!!!!! uploading for ya now

I'd aim for 1.2 bar. 1.0 is a bit of a waste of time as it just overfuels.

I'd aim for 1.2 bar. 1.0 is a bit of a waste of time as it just overfuels.

Yeah am aiming for 1.2 but I still keep hitting this "decat or not decat" issue.

Why does 1.0 overfuel? Does the ECU overfuel by default or something? I'd imagine anything >1.0 is a bit of an unknown quantity as the ECU doesn't even see it and just fuels for 1.0 bar...

*vid*

http://media.putfile.com/Exhaust-51-42

Yeah am aiming for 1.2 but I still keep hitting this "decat or not decat" issue.

 

Why does 1.0 overfuel? Does the ECU overfuel by default or something? I'd imagine anything >1.0 is a bit of an unknown quantity as the ECU doesn't even see it and just fuels for 1.0 bar...

Decat mate, no question about it. I wouldn't want any cat in there above 1.0 bar.

Yep, it overfuels as stock, at 1.0 bar it will be rich which means you're not getting the most from the car. It will be at 100% duty cycle (more or less) at this, so raising boost further just brings the afr a little leaner.

IME, the only spot to watch for is when the 2nd turbo starts to spool, around 4.3k rpm. It will still be rich from 5krpm to redline.

Get an AFR gauge if you're worried (its a good way to learn how your engine is working once you get used to it), they're very cheap these days.

IME, the only spot to watch for is when the 2nd turbo starts to spool, around 4.3k rpm. It will still be rich from 5krpm to redline.

 

Get an AFR gauge if you're worried (its a good way to learn how your engine is working once you get used to it), they're very cheap these days.

Will do. I have just been informed my EGT/AFR and oil temp gauge has been dispatched so this will be going in soon.

Think I will de-cat, go visit powerflow to get an inline non-restricting muffler in, and worry about my MOT in a years time!

*vid*

 

http://media.putfile.com/Exhaust-51-42

Nice, thanks! I like it!

Had some vids of my car but obviously not from behind like that.

Cheers

You can always stick the 2nd cat back in for MOT time... or find a friendly MOT centre

You can always stick the 2nd cat back in for MOT time... or find a friendly MOT centre

Therein lies the issue - there's nowhere for the 2nd cat to go, even if I had one to put in - I don't

James

Therein lies the issue - there's nowhere for the 2nd cat to go, even if I had one to put in - I don't

 

James

Just re-read your first post. Whoever told you to keep the first cat in needs their head read - respected member or not!

Why don't you do what most do: Get a 2 piece decat pipe, one decat to replace the first, another to replace the 2nd, then come MOT time just stick your original cat back in. Unless I've missed something here (probably!!).

If you don't already have a 2nd decat, just ask, someone will give you one (even have one here you can have), it's not like they ever get sold.

Just re-read your first post. Whoever told you to keep the first cat in needs their head read - respected member or not!

I'm sure he will see this thread

Why don't you do what most do: Get a 2 piece decat pipe, one decat to replace the first, another to replace the 2nd, then come MOT time just stick your original cat back in. Unless I've missed something here (probably!!).

I think you're missing the fact that I have a custom stainless steel pipe going from the 1st cat right to the back of the car, although I will have to get the car up on ramps to verify this. To put a 2nd cat back in may require cutting out a section of exhaust

I'm sure it was just a misunderstanding

I think you're missing the fact that I have a custom stainless steel pipe going from the 1st cat right to the back of the car, although I will have to get the car up on ramps to verify this. To put a 2nd cat back in may require cutting out a section of exhaust

Yep, missed that! You have a problem then. You shouldn't keep the first cat in place with 1.0bar and above due to heat retention, but then that might be a little loud. Maybe just get an extra silencer fitted to your pipe - a small straight-through one should be suffcient to take the noise out, it'll certainly do as much, if not more silencing as your cat is doing now.

You shouldn't keep the first cat in place with 1.0bar and above due to heat retention

How much of a PITA would it be to re-fit the 1st cat for an MOT? I am guessing it attaches straight to the back of the turbos which sounds like a nightmare...

How much of a PITA would it be to re-fit the 1st cat for an MOT? I am guessing it attaches straight to the back of the turbos which sounds like a nightmare...

It's possible, but is more of a PITA than the 2nd. My local Kwik fit charged £20 to replace the 1st cat, £10 for the 2nd.

It's possible, but is more of a PITA than the 2nd. My local Kwik fit charged £20 to replace the 1st cat, £10 for the 2nd.

Blimey. That's bloody good value!

I'd happily pay £20 rather than spend a morning skinning my knuckles and generally swearing a lot