alternate way to BPU?

For almost a year now I have run without cats and no FCD. This of cause resultet in a lot of annoying fuel-cuts. I was about to go the standard way of adding a FCD, R-ring and a fuel pump to deliver the extra needed fuel.

Im wondering of it being possible to hit BPU like power with another angle. Would there be anything in the way of adding the original first cat and thereby limiting the boost to around 0,8 - 0,9 bar and then adding a boost controller to push to 1,0 - 1,1 bar which I know my current fuel system supports (fuel-cut used to happen at 1,1 - 1,2 bar at which point everything ran fine after I replaced the spark plugs).

I would prefer this way since I might be able to get me a cheap boost controller as well as having the ECU fuel-cut still in place gives me peace of mind and saving me from boost spikes and thereby stress on the turbos, which I would like to keep running happy.

I have no plans or wishes about going above normal BPU since this is my daily driver and here in DK virtually all cars are slow ;-)

If you limit the boost with the first cat and then up it to 1.1 or whatever, you'll still get fuel cut, if the ECU sees more than 1 bar, you'll get it.

How do you *know* your current fuel system can support more than the stock amount of boost? Do you have an air/fuel mix gauge or anything like that?

I think just upping the boost without uprated fuel pump is a little dangerous... fuel pump is only £80 and can be fitted yourself...

Also wont you have problems with excess heat near the turbos, due to the 1st cat, if running higher boost...?

The EGTs will be higher. If you wish to limit boost and have the flexibility of increasing boost with an EBC.

Just get CW to make a 1 bar restrictor ring .. and then you can increase the boost with an EBC to 1.2 when you need to.

If you limit the boost with the first cat and then up it to 1.1 or whatever, you'll still get fuel cut, if the ECU sees more than 1 bar, you'll get it....

My fuel cut is at 1,1 - 1,2 according to my quite trick boost gauge. 1,1 being the standard cut as far as I know and have read many places.

How do you *know* your current fuel system can support more than the stock amount of boost? Do you have an air/fuel mix gauge or anything like that?

No gauge, but I have run with out cats hitting the fuel-cut at 1,2 bar several times. All is well at that level. I know it is close the the limit though which is why I would want a boost controller to push max 1,0 - 1,1 bar

I think just upping the boost without uprated fuel pump is a little dangerous... fuel pump is only £80 and can be fitted yourself...

You might be right. The point here was to keep the fuel-cut for peace of mind and the power i'm putting down just below fuel cut is good enough for me So adding an walbro but keeping the cat would that work out?

Also wont you have problems with excess heat near the turbos, due to the 1st cat, if running higher boost...?

Dunno about the temp. I can certainly understand the theory. Does anyone have expiriences with this specifically?

I guess it may be different from car to car but my fuel cut always happened when I strayed over 1.0 bar for a few seconds. It's when the ECU sees a certain voltage from the MAP sensor, so if it's slightly out then you'll get fuel cut at a slightly different point.

You're correct about the fuel pump and gauges not being *required* for BPU, but it's all about mitigating the risk. You ran 1.2 bar, and said all was fine, but who's to say you weren't running dangerously lean and if you'd kept going another few seconds you could have damaged the engine?

Perhaps someone more knowledgeable will correct me if I'm talking crap, but I think that's the main reason most people do BPU in a certain way.

Also - the best FCD (Thor/TRL, secondhand £40) allows you to set the new fuel cut threshold at another level, say 1.3 bar so if something does go wrong you'll still get fuel cut.

Thanks, cheeky ;-) You're probably right about this I'm sure. Which is why i'll look into the pump thing before doing any excessive boosting. Already got the FCD lying around just havent fittet it.

Now, how about that thing with running bpu boost WITH the first cat in. anyone?

Now, how about that thing with running bpu boost WITH the first cat in. anyone?

I have asked this before as I'm in the same position... some people said it should be OK, but most said it's not a good idea, mainly due to the higher temps that would be reached.

For me the *only* advantage in having the first cat in is that it's limiting the noise. I will run it without, and see what happens.

Looking forward to other's comments though!

I would imagine the better option would be to replace the 2nd cat rather than the first,this may let you boost to your 1bar(ish)

without needing a boost controller.

This will also move any extra heat further away,reducing the risk of high egts.

Ooooh... that sounds interesting. The second is less restrictive? I wonder why my supra-fixer suggested the 1st then...

Also - the best FCD (Thor/TRL, secondhand £40) allows you to set the new fuel cut threshold at another level, say 1.3 bar so if something does go wrong you'll still get fuel cut.

Not strictly true, it allows you to set it to just under 1.2 bar I believe. You can't set it to anything over 1.2 bar as it just removes the cut altogether.

So are the 2nd cat less restrictive than the first? Is anyone running with just the 2nd cat in? how high does boost run with just that and a complete 3" system?

I'am running with the first cat in egt's sit at 600 normal cruising at 70/80,when giving it some egt's rise to around 700 I'am sure some one will corect me if i'am wrong but i think this is still within the limit? I can also run 1.2 bar no problem although I do have FCD and Walbro pump fitted.

So are the 2nd cat less restrictive than the first? Is anyone running with just the 2nd cat in? how high does boost run with just that and a complete 3" system?

Yes the first cat is the most restrictive, this is fitted mainly for cold start emissions, the second cat general driving once up to temp.

All cars differ, some will boost high other lower, you'll need to try it and see. If it boosts over 1.2bar then you'll need to fit a restrictor ring to lower the max boost.

If you do leave the second cat in then I would definitely fit an exhaust gas temp gauge so you can monitor temps.

cheers

I'am running with the first cat in egt's sit at 600 normal cruising at 70/80,when giving it some egt's rise to around 700 I'am sure some one will corect me if i'am wrong but i think this is still within the limit? I can also run 1.2 bar no problem although I do have FCD and Walbro pump fitted.

Where is your EGT sensor fitted, before or after the turbo? I suspect by the readings you're getting it will be after the turbo.

Usually the temps after the turbo are around 200C cooler, so 700C is around the max you would want to run at.

nige, let know its getting to be a really interesting post this

- and thanks Nic! Just to make sure I understand you, leaving the second cat in is still better EGT-wise than leaving the first in, right? If I get myself an EGT gauge, can you recommend me one? Would it be better to go for a DEFI solution since i'm also a bit hot on a oil temp and pressue gauge.

- and thanks Nic! Just to make sure I understand you, leaving the second cat in is still better EGT-wise than leaving the first in, right? If I get myself an EGT gauge, can you recommend me one? Would it be better to go for a DEFI solution since i'm also a bit hot on a oil temp and pressue gauge.

Yes the second cat furthest away from the turbo, would be the better one to leave in, if you do want to keep one.

I use the Defi gauges, there are a lot of different brands and models of gauge available, the Defi's are my personal favourite. Let me know if you would like any details/prices.

Behind the turbo Nic,didnt fancy the risk of crap going through the turbos by drilling holes.

Behind the turbo Nic,didnt fancy the risk of crap going through the turbos by drilling holes.

700C is around the max you'll want to push it too then, over this and it starts getting into the danger zone.