Hi all,
Anyone know how to detect a minor boost leak?
I think standard boost is 10-8-10 psi approx?
I have a Greddy boost guage which reads 12-8-10 on WOT, but when the second turbo kicks in it reads 14 for a split second (which gives a very nice kick) then straight back to 10, then gradually drifting down to 8 and losing power very slightly.
The questions are:
Should it be boosting upto 14 psi momentarily as the second turbo kicks in?
If the first turbo holds 12 psi untill 4500 rpm ie. there\'s no boost leak, then why does the second turbo drift down from 10 to 8 psi?
Any opinions appreciated, the car is basically stock, done 5K on a re-build by Tim, feels very quick but would be nice to hold 10 psi and even quicker!
Also, thinking about it, why does 10psi after 4500 rpm give more power than 10 psi before 4500 rpm, I mean if a small turbo or a large turbo both produce 10 psi of boost why is the big turbo quicker? Probably a stupid question but I cant get my head round it lol.
Cheers,
10 psi after 4500rpm give more power than 10 psi below 4500rpm due to the fact that the engine is revving faster which burns more fuel & air than lower revs. basically your getting more \'bangs\' per minute
14psi sounds like boost spike so be v careful as you could/would be running lean
Whilst at WGT I was bugging Pip about some boost curves he was getting on my single and he showed me typical boost curves for a stock twin.
The boost surge you feel is the boost catching up. When the 2nd turbo initially kicks in, you get a drop in boost for a split second as the pressure drops. Then the boost picks back up to its orginal curve and carries on.
If you think you have got a boost leak, look for oil on the pipes around the joins. It usually sprays out under pressure and is a good tell tale sign.
Adrian
(PS. Go single...you know you want it!!!!)
The reason why 10psi after 4500 rpm gives more power than before 4500rpm is biecause there are two turbos producing that pressure, not one.
so basically, you have the same pressure, but twice the volume of air. It\'s not quite that simple as twice the air, but you basically have two turbos putting 10psi of air into the engine, instead of one turbo trying to get 10psi of air in. That\'s why there\'s more power.
So, 1 big turbo producing 10psi pressure, will also produce more power than a small turbo producing 10psi of pressure because it can put more air volume under that 10psi of pressure.
Gettit? :)
Have you spoke to Tim about this. He is the best person to discuss this with if he built it and knows what you system consists of
Scott
You boost pattern i do not think is anything too much to worry about.
Firstly, your change over. Yes, the boost is spiking momentarily rather than dropping. I believe this is a mod that can be made. I think i have had this done, as i have the same thing - when i first took my FD to PIP at WGT to have a boost problem fixed, i had a change over which dropped in pressure. Then i took it to WGT for a second bit of work, and now it peaks when it changes over, to a similar amount to you. So, i think this is not a serious problem - ordinarily, a boost of 14 psi would be bad - but it is only being done for a split second, so not a massive worry for you. I warn you though - i may be wrong! But i am not worrying about mine! Mine has been checked over by WGT!
Secondly, the trailing off of you boost is basically normal. It can happen at higher revs at full boost - i think it is a safety thing, but again am not 100% on that one. But i do know that it is a normal operation of a boost pattern at higher revs. It can trail off!
Thanks for the replys everyone,
Yeah i get it now Nik :)
I was a bit concerned cos my last FD (black one in pic) held it\'s boost all the way to the redline but it did have an Apexi PFC and this one doesn\'t. This one feels quicker tho probably cos the last one had 65k on the clock and compression wasn\'t so good?
I\'ll have to update my pic, here\'s a pic of the new one,