dudical26

iTrader: (17)

Well I have been reading more and more about people running high boost on pump gas 93oct with a Evo IX with stock turbo.

I want to pose the question to fellow tuners, how much boost do you run on pump gas. Please list car model and turbo.

I used to run 21-22 but have recently been running 25psi on pump. I have timing of 4 degrees at the boost spike, and little to no knock. How much more room is there?

TouringBubble

iTrader: (2)

I have run 25 psi on 93. IX on stock 10.5 turbo. 3* to 4* at peak torque.

I'm currently running ~24 psi daily on 93. But, I've got a tapering boost curve, so I peak at about 25.5 and taper to about 23 @ 6200 or so. I call that 24 psi based on a rough average.

I also don't drive very hard on the street.

dudical26

iTrader: (17)

that sounds very close to what I run. Its a 25psi spike and I hold ~23.7 @6200
Have you tried running more?

RazorLab

iTrader: (8)

Believe it or not I have seen 26psi on a Evo 9 on 91 octane, no knock, 2*-3* advance at peak torque. This Evo had ported exhaust mani/turbo hotside, tubular 02 housing, GM solenoid, exhaust cam gear, TBE no cat, cosworth cams.

If it was my personal car, I would have left it at that. Dropping it from 26 to 24psi it lost 18wtq. From 340wtq to 322wtq, on a low-reading mustang dyno. That wtq is usually reserved for 100 octane tunes on this dyno.

Boltz.

iTrader: (42)

I've pushed the boost quite high on pump gas, and although in theory it sounds like a good idea to make you go faster, you don't really go faster at the track because the car won't make that kind of boost in the upper RPM range. You can keep increasing boost but you will (obviously) have to lower timing to compensate, its all a trade off and you just need to find the sweet spot for your car. If it makes the same amount of torque on less boost and more timing as opposed to pushing the threshold for max boost, then go with the lower boost level as there is no point in pushing the turbo/intercooler any harder than you need to.

Are you doing this to try and make the car faster in a drag scenario or just looking for more torque?

Boltz

mplspilot

iTrader: (7)

Since i'm not a real tuner, i'll quote one:

BenJ

iTrader: (21)

i'm running 23 pounds on 91 with 0 counts of knock and very conservative AFR's. Not too sure on the timing though.

dudical26

iTrader: (17)

Yea I saw that thread, and that is what made me want to start this one.

dudical26

iTrader: (17)

I'm doing it for both street TQ and drag racing. The TQ on the street is way higher at 25psi and 4* then it was at 22psi and 7* And for daily driving TQ kicks a**.

On the track I know the spike wont help aside from maybe during 1st gear. Other than that I never drop below 5800, I suppose having 24psi at 5800 might do better than having 22psi there. I'll have to try it,

Asmodeus6

iTrader: (7)

21-22psi 93 oct
high 10's creeping to 11~1. a/f.
timing I can't say for certain, stupid laptop never stays running.
Should be around 8*

No knock.

dudical26

iTrader: (17)

thats pretty rich. Although that is more timing than I am able to run. But I run AFR of 11.5 at boost spike and then 11.8after that untill redline.

Asmodeus6

iTrader: (7)

This is still a preliminary tune. I am personally still learning ecuflash and it was more about getting the car to predictably DO what I want, than my A/F of choice. Truth be told, the car still feels flat on top. It likes itself drowning in fuel. And more timing. To which, my wallet simply cannot abide driving nearly 100 miles a day in this thing. I haven't been able to duplicate my preferred a/f timing curve during spoolup because of lean spool being unpredictable at times. But I don't run cars as lean as you do. I learned that lesson years ago.

One spurious knock spike at 12~1 at wot & full boost turned two of my exhaust valves into crayon. Then later a piston into puzzle pieces. This was a DSM. But still. Ever since, I've run it fatter... and kept my timing up. And always feeding it gas at peak boost. I keep motors in cars alot longer this way.

Timing ~ Boost ~ Lean
Pump gas = Pick two

l2r99gst

iTrader: (2)

30-32 psi for a fraction of a second? What's the point of saying the car runs 30-32 psi when it is a very short spike. Tell David to post some boost logs and I can guarantee that the boost is no more than 23-24 by redline, maybe even 22.

I saw that thread, too, and I think that a lot of people are reading way too far into it. You can run whatever boost you want, adjusting timing accordingly. You just have to find what is the best for your particular setup, meaning what changes continue to increase acceleration without introducing knock.

The main car in question was a HTA35R car. 30 psi on that turbo is a world of difference from a stock turbo that struggles to spike to that. The 35R can hold that psi no problem and is very efficient at that psi. The stock turbo would struggle to hold 23-24 psi to redline. Spiking to 30 psi and maxing out the stock turbo is just blowing a ton of hot air. Notice how the cars running that boost also had every possible mod to increase VE and lower temps as much as possible, like big ICs, cams, race heads, AEM (speed density), etc.

Just from that one thread, I can see a lot of ppl blowing up their cars, trying to run 30 psi on pump gas. Heck, if David said he does, it must be OK, right?


Eric

dudical26

iTrader: (17)

In general when you quote how much boot you run. You refer to what you spike. Everyone tapers down to ~20 on stock turbo by redline. The midrange is really the only place you can hit high levels of boost.

l2r99gst

iTrader: (2)

I agree with you, but this generality comes from the fact that many people here are so used to the stock turbo. As we all know, the stock turbo can't hold much more than 23 psi or so at redline (depending on VE of your setup), so people do tend to quote their boost spike.

But, if you notice, many more people now quote their spike and boost levels at varying RPM, which is much more descriptive for a relatively small turbo, like our stock turbo. I'm just saying that DB could have easily said his brother spikes to 30-32 psi, rapidly falling to 22 psi or so, because I can guarantee you that there are a million noobs reading that thread thinking that they can now run 30-32 on their stock turbos all the way to redline. And even worse maybe do something stupid like unhook their wastegate to try.

Personally, when I quote boost levels, I'm used to bigger turbos, so I quote the boost that I ran and held to redline. It all depends on what you are familiar with.


Eric