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How much boost should I run?

3K views 29 replies 12 participants last post by  4Jenna 
#1 ·
I have the on3 70mm kit for my 94 cobra. I want it to last more than a summer with the stock bottom end. Right now I have the WG set up for 12psi but am thinking maybe back it off to the 10psi set up. I would like to see 450-500rwhp with the downpipe open.

My set-up, the main stuff

Blueprinted 92 shortblock
GT40 heads (completely worked over flow about 220-230cfm on the intake)
xe276hr cam
cobra intake, polished lower
ARP Head studs w/9333 gaskets
70mm tb
60# injectors
255lph intank plus trex
 
#3 ·
Its hard to say. If it were mine I'd have it tuned. Run the lowest boost possible to get to 450rwhp and stop there. Lots of guys running more with no problem. Others have not been so lucky. You just never know how far you can push a stock block car. 4.6psi and 497 rwhp split my nice new 331 right down the center in under 100 miles.
 
#8 ·
Its hard to say. If it were mine I'd have it tuned. Run the lowest boost possible to get to 450rwhp and stop there. Lots of guys running more with no problem. Others have not been so lucky. You just never know how far you can push a stock block car. 4.6psi and 497 rwhp split my nice new 331 right down the center in under 100 miles.
So you are saying you would want to run low boost and a bunch of timing on pump to reach your hp goal? That mindset is probably why your 331 didnt last. Makes more sense to run 2-3 more psi and bring the timing down.




12psi is a bit much for the stock block; I run the smallest wastegate spring alone (4psi) and have a simple $20 Ebay manual boost controler. I have this set at 7psi under full load in 3rd gear (AOD). Not sure on the HP, but feels like 400-450ish. I'll have a 1/4 mile time in the next month or so. Maybe a dyno run, just to be cool.

I would not run more than 7-8 psi if you want to keep the stock block alive.
Quit being scared.
 
#4 ·
12psi is a bit much for the stock block; I run the smallest wastegate spring alone (4psi) and have a simple $20 Ebay manual boost controler. I have this set at 7psi under full load in 3rd gear (AOD). Not sure on the HP, but feels like 400-450ish. I'll have a 1/4 mile time in the next month or so. Maybe a dyno run, just to be cool.

I would not run more than 7-8 psi if you want to keep the stock block alive.
 
#7 ·
How the hell are you tuning your car after you put a turbo on without dynoing it? Please don't say a wideband and street pulls...

Using a Quarterhorse and entering known settings for my injectors and MAF. Yes I did tune it from driving around under normal conditions, not on a dyno. I made sure the timing and fuel were safe before going into boost.

In fact my wastegate was hooked up wrong and I was seeing 15psi a few times, lucky I had safe fuel and timing figured out. Now I have the smallest wastegate spring in the gate and adjust it accordinly; currently at 8psi.
 
#13 ·
I can tell you this much. I ran 9 and 13 lbs on a bone stock 95 Cobra. I had it tuned and everything and it made 413 / 525 at the wheels on 13lbs. If it wasn't for my tinkering and me frying the Digital 6 I'm sure it would have lasted quite a while. I am planning on running 13 lbs again with my new setup. Hoping for 450 / 550 at the wheels this time.
 
#15 · (Edited)
Id rather run the lower boost level and more agressive on the timing. Much more efficient and you waste less fuel.

Just because someone blows their motor up by going to agressive on the tune is their own fault for not tuning it right, you cant blame the methodology behind it, its no different that somone blowing their motor up with more boost.

Your tune is either safe of its not.

Not that it really matters, itll make the power whichever way you go, less boost more timing or more boost and drowning it in fuel and pulling timing.

So its up to the person with the car.

Not too good IMO when you got your motor all jacked up with boost and got it pig rich and hardly any timing in it and you get waxed by a similar setup running less boost and a real tune in it.
 
#25 ·
I street tune my junk , 11 psi 22deg timing locked out and 11.2 afr's . Works for me , i fine tune at the track so im not flying up and down the road with the wideband in my hand lol
 
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