View Full Version : Darned cats again!
I'd be grateful for some thoughts on this. Took my car for service at Option. No problems with that as such.
He noticed the car would overboost, recommended I replace 2nd cat asap to stop engine achieving meltdown.
I know it will overboost, you have to stamp on the accelerator & hold it there to warp speed to achieve it , but I have seen 1.8+ (briefly!) & detonation. Simple cure, I drive it in a way that doesn't make it happen - it's still quick enough! I want at some stage when I am solvent again to look at fuelling, cooling etc etc & try & sort it out.
However, main question is, he assures me the car will drive better with 2nd cat in & I will not lose power - I think this kind of contradicts most of what I have read to date?
I also have GreddyProfec-B boost controller which I THINK controls boost to a degree, but not if you really boot it.
He also said the only option to cure overboost was cat replacement or bigger turbos - ?
I know this has been done before to a degree but I couldn't find anything which really answered the question.
You could try BJs 2.5" restrictor to keep boost low, or you could get some hybrids!
Thats about all I can think of.
Can't afford the hybrids at the moment! ^:sad: I wondered about the restrictor, can that be fitted in anything? No idea what cat removal pipe I have.
I think BJ & CW wold know about its fitting, and on a budget, I think it would be the only option, since they only other ways would be the hybrids or a bigger wastegate which are way too expensive :(
Chris, BJ - any clues? What about leaky pipes, is that likely? How would I tell?
The restrictor idea is (AFAIK) a disc of metal that sits between the two flanges at a join in the exhaust, the only way it wouldn't work is if you have sleeve joints all the way through? Never actually seen one so I'm guessing.
I've read of overboosting being caused mainly by wastegate problems in J-specs, but I guess it wouldn't hurt to check all your pipes and associated gubbins.
The car will be all boring and quiet if you put the cat in! You don't wnat that!
I'd say your boost controller was set up wrong. In Blitz BC terms the gain is up too high, causing spikes. Which means its over spooling whilst trying to hit the boost level you've set.
I don't know what the GReddy unit does but I know the Profec isn't too happy about sequential twins on the whole when running in its dynamic mode, best to have it one manual mode.
If you're not running a decatted exhaust there is no other answer. IMCO (C = current ;) )
Try turning the Profec off and see what happens this could rule it out or in.
Leaving the cat in will increase lag more than it cuts power.
hope that helps
I've ben wondering about wastegates; need to get a bit more clued up on all this & do a bit more tech reading!
Cat in = boring quiet car with more lag...oh good NOT
The Profec unit I have is not the fuzzy logic one, it just has low & high & sharp to mild. Very difficult to fathom out what (if anything) it is actually doing. I have been running it turned off lately, doesn't seem to make a great deal of difference. If I turn it right down the car feels sluggish.
I really need to throw away everything that came with the car & start from scratch I think!
I was just confused with the idea of the car running better & not losing power with the cat back in. Never driven one with cats.
Poor chap was probably just trying to prevent stupid woman frying her engine!
So what have you got in the de-cat department??
HKS front pipe?
Blitz dwon pipe??
What I'm guessing is that they are too big for the stock turbo's.
I think if you are getting major peaking and it's not the unit you should consider changing to Chris Wilson's 2.5" de-cat pipes they, I believe, will only really let you hit 1.4bar max without a boost controller.
If you are running a decatted car on stock turbo's you don't really need the boost controller.
Wastgates possibly one has been jammed shut? This would mean it couldn't regulate the boost properly. Ian C has recently had his turbo's off and could propbably give you some guidance on this matter.
Has it been happening long??? Have you changed anything? No, then something might well have broken...
Cheers
(Edited by Alex Holdroyd at 11:33 pm on Feb. 21, 2002)
Hey Franx
I take it you are running with both cats removed?
As I understand it a lot of imports overboost with both removed .(I'm running with one and no probs)
So , as Alex said, the boost controller aint gonna help as it can't lower the boost level only raise it.
Its down to the size of the wastegate (too small) on j'specs.
If you put the second cat back in , I don't think you'll find the lag a problem. Then when the overboosting is cured , you can set the boost controller to limit maximum boost to something sensible like 1.2bar .
HTH
I have the same problem, my car is boosting to 1.5 bar and has detonated, so i was going to put the second cat back on. But at the moment Chris Wilson is making me a plate to put in the exhaust which should bring it down to 1.2. And if i find this is not enough, i will mod the plate to have a bigger dia hole till it is right for me.
I am hoping to get it on this weekend, i will keep you up dated on how it goes.
Quote: from matt on 12:11 am on Feb. 22, 2002[br]Hey Franx
I take it you are running with both cats removed?
As I understand it a lot of imports overboost with both removed .(I'm running with one and no probs)
So , as Alex said, the boost controller aint gonna help as it can't lower the boost level only raise it.
Its down to the size of the wastegate (too small) on j'specs.
If you put the second cat back in , I don't think you'll find the lag a problem. Then when the overboosting is cured , you can set the boost controller to limit maximum boost to something sensible like 1.2bar .
HTH
In theory the boost controller cannot control the boost down, but in practice Leon can make it bring the boost down by a couple of PSI. Its all a question of pipework and setup.
I think what Option are saying is that you could put the cat back in and bring the boost down and still get the same level of performance as the turbo would then be back inside its efficiency range. I know my car running at 20psi is operating outside the turbos range but Im willing to accept that and just keep a close eye on the boost.
JB
I did speak to Leon about the controller, it does seem to have some effect but with no 'read-out' on the unit it's difficult to judge accurately just on the boost guage. I want to replace it with a better one at some stage.
I understand what you are saying about efficiency range, & you can actually feel that it is not producing any more power by pushing the boost beyond about 1.4. Option said up to 1.3 is OK on stock turbo's, anything beyond that risky & not productive.
I don't know what pipes I have, everything (apart from new dump valve) came with the car from Japan.
It is not causing me any major grief at the moment, I can't afford to spend money on the car for a while - if I can get hold of a 2nd cat I will perhaps put that on out of interest, but I assume if I don't thrash it & get high boost it's not a problem for the car?
Bolts, I'd be interested to hear how you get on with the restrictor. As you say this is a fairly easily customisable mod.
Thanks for the input all, & if anyone has a cat for sale let me know & I'll maybe try that. No idea what they go for 2nd hand?
Some are usually on sale on Ebay or Supraforums, usually about $300.00.
Brian Jackett
23-02-02, 18:18
Bolts just fitted a Chris Wilson restrictor plate it is even adjustable. Bolts Supra was boostin to 1.5 now down to 1.275 ish.
30 min job to fit.
Ring CW and talk to him he supplies restrictor and all gaskets for approx £30. That will sort your problem.
Bolts can use full throttle now , oh my God!
regards
Like Brian has said it took 30 mins to fit (easy job) and even though boost is less, it is faster as i can plant my foot flat to the floor. And i do not have to worry about what it is boosting to and it does not det. at all.
Brian Jackett
24-02-02, 15:26
That is good
Andy Metcalfe
24-02-02, 15:42
Fran,
I have a cat - if you want it mail me.
THOR Racing
25-02-02, 14:02
Franx,
I've been trying to get hold of your regarding your speedo converter.
I've tried francesca@supradriver.com (which bounced) and francesca@parravion.freeserve.co.uk (which I never got any replies to)
Please email peter@trlperformance.com (or SMS/tel me on 07802 412969) Sorry lost all your details when my PC died a few weeks ago.
Regards
Pete
Pete - sorry, I too have had computer probs, received an email from you & will reply asap!
BJ & Bolts, thanks for that, will speak to Chris..sounds as if it would sort my problem. Foot on the floor - sounds OK to me..!
Andy - would like the cat, will mail you too.
Thanx guys! ^:cheesy:
vBulletin® v3.7.3, Copyright ©2000-2008, Jelsoft Enterprises Ltd.