Hey Chaps,

What is the max boost I should be attempting to run on the following evo configuration:

98RON (93oct in USA speak)
stock o2 housing
3" down pipe
stock cat
3" catback

Cheers
D.

 

I run about 24.5 PSI normally and 29 PSI with water/alky injection thanks to V5. I think it would be worth your while changing to a high flow cat.

 

23psi on 93 Octane. You can spike a little higher on spool up with no issues, but I wouldn't push it too far on pump gas. I've read some of the posts by members who shall go unnamed running much higher boost using AEM EMS, but they aren't exactly stock motors...

 

yeah basically its a stock car, with the exception being the exhaust..

so 23-24 should be fine, for peak and tapering to 20psi, or will the stock turbo be able to push more efficiently at redline?

 

With the addition of an O2 housing, decat, walbro, airbox mod I hold 25 psi to 6000 rpm. Mid is the same in summer, higher in cooler weather or using meth (29 psi). 99 ron, raised fuel pressure to 3.6 bar by modifying oem reg with a hammer and testing with a gauge. Works great and has done for 30000 km. Gives the idc headroom to add 10 % meth in the gas tank.

 

so 25psi is safe(ish) for the stock head, stock internals?

wow...

 

Yes. The fq360 spikes at that with an exhaust including high flow cat, fuel pump, 3 yr warranty and capability of running safely on 95 ron.

 

reckon I can probably not worry bout the FP...

ok well ill tune for 24psi then...

 

I max the injectors at high revs at standard fuel pressure at 11.5 afr even with the walbro at least in cool weather and without meth. They go static at about 94% idc - ie I lose afr control. Depends how hard you try with top end boost but there is more top end than many realise. With more restricted breathing or not trying hard to hold top end you will prob be ok.

 

understand, watch the IDC's.

I was more worried about popping the head off or something.. stock headstuds..

 

higher boost often equals a loss of consistency between runs due to the excessive heat. It's best to experiment and figure out what's best for your car.

 

mm for track I would probably just 20psi flat.

for street I would run 24psi so back-to-back runs probably wouldn't be a problem

 

With the stock CAT I think you will have trouble pushing beyond 23 psi. That is your limiting factor at this point. If you can run more than 23 with little knock then thats great, go for it.

If you really want to run more than 23 on pump gas I think you will need a test pipe or very good high flow cat.

 

100cps mil.spec good enough? :P

 

23 psi down low (till about 5k) is probably fine, but any more than about 19 psi at 7k will be hard for the turbo to handle with the stock intake/cat/O2. Add about .5 psi up top for each of those you get rid of.

I did some back to back testing to see where the stock turbo was most efficient on my setup (tubular mani, SS O2, 3" DP, 3" TP, 72mm Cat back, cone filter, 3.5" FMIC) ... I tested:

26 psi down low and held as much as possible at redline
24 psi @ 3500 and 21 psi @ 7000 (taper starting at 5500)
21 psi @ 3500 and 19 psi @ 7000 (taper starting at 5500)

The 24 psi tapered to 21 made more power across the board than the other 2. The 21 psi run only lacked about 5 ft/lb tq and basically followed the same curve as the 24 psi run till about 5800 then the hp and tq dropped off a little. The 26 psi run made about 2 ft/lb more tq peak but the curve plummeted afterwards due to the heat.

I decided on 23.5 psi till 5500 tapering to 20.5 psi @ 7000 for my street tune. It works great on the street, but it does heat soak if you try to hot lap the 1320. It has a little too much tq for autocross so you've got to go a little easy out of the apex at times. I wouldn't run this aggressive for a road course tune.

Hope that helps.