Is there such a thing as too much boost?

[Brickell FIST]

What would be considered too much on 93 and E30?

Stock turbo?
Hybrid?

What can happen if it goes beyond?

Thanks

 

[OffTheWall503]

It all depends on the conditions, fuel, tune, etc. But it seems the stock turbo craps out around 27+ PSI? You can technically tune it to whatever boost you want but at some point you'll be outside the range of effective efficiency.

 

[letitreign]

What do you mean by the stock turbo craps out at 27 PSI? It can't move enough air beyond that? How does the engine handle this high of a pressure?

 

[OffTheWall503]

Somewhere around that pressure the turbo loses efficiency which hurts performance and longevity at that point. Each turbo has an optimal range of pressure and efficiency.

 

[Crooked Letta]

https://en.wikipedia.org/wiki/Compressor_map

Watered down version, but it basically boils down to ratios. There is a happy medium for everything, with turbo's you get a decent sweet spot. If you have ever seen a graph that looks like a mountain on a turbo vehicle this pretty much dictates a turbo being maxed out. Livernois maxed out the EB 2.3 on the Mustang an achieved something like 428WTQ but it was all downhill after that, and this is basically a turbo following that choke line.

Pressure is a loose term or boost if you will. It tells a fraction of the story in terms of power. Flow is more accurate and here is why. As stated before timing and fuel make a difference. Lets just say you have 20 PSI @ 100 degrees F, there will be a big difference between this and 20 PSI @ 0 degrees F. This is where flow comes in and not only are you running the same pressure, but you are flowing more air, at that cooler air. Two fold effect, more air, more fuel, more power, but also cooler which will loosen up timing a bit as well. Same PSI but you can bet on a 10%+ difference in power.

On the flip side Boost can be used as a reference when comparing things like Dyno's. You can compare how different turbos spool and how they follow the surge/choke line. You see this when comparing stock turbos to BT's, and how they build/keep boost.

 

[Sourskittle]

PEAK boost numbers mean very little on our stock turbos. It's a giant spike of torque that almost instantly disappears ( someone posted a V-dyno recently that showed this, the torque fell so fast, his V-dyno dropped by 20-25ft. Lbs simply by changing the smoothing setting. Which means, if it was making xxx torque, it was only doing it for such an extremely short amount of time, that when averaged over fractions of a second, it's dropped A LOT.

What you guys should really be looking at is boost at 5300-6500rpm and how much/how fast it falls.

The idea with the stock turbo is to let it make its power where it can down low, and when you get to the higher rpm's sacrifice boost for cooler/consistent power using timing advance.

Think..... turbo power from 2900-5000rpm and then Honda/Vtec power from 5300-6200rpm.

Also gotta stop looking at PEAK numbers as a total result.

The V-dyno I mentioned was actually a beautiful power band for the stock turbo. Made 200whp~ for a HUGE chunk of the power band. PEAK numbers be-damned, it didn't need the spikes for "PEAK numbers". It looked GREAT no matter the actual peaks.

Also. The stock map sensor maxes at 29.4psi. I made 354ft. Lbs of torque on a stock turbo way way down low. But after the instant donkey
Kick, the car just felt like
Crap again almost instantly again.


Sent from my iPhone using Tapatalk

 

[Brickell FIST]

X37 on E30 hitting peaks of 29 psi outside of efficiency? 27-28 average.
On 93 26-27 psi. I'm just seeing is this cause for concern. What is the most you guys have seen on a hybrid?

 

[Sourskittle]

X37 on E30 hitting peaks of 29 psi outside of efficiency? 27-28 average.
On 93 26-27 psi. I'm just seeing is this cause for concern. What is the most you guys have seen on a hybrid?

Nothing wrong with that at all. But again, peaks are not as important as what it's running on the top end.

I maxed out my map sensor on a regular bases on my OG cyborg ( 29.4psi ) and held 26-27psi to redline to make 290whp. With the cyborg39 I expect about the same but making more power of course.

Just realize that 27psi at 3600rpm is a HUGE difference compared to 27psi at 6500rpm. So when you say "I run 30psi" that could be perfectly fine at 3600rpm. While the same "I run 30psi" at 6500rpm is not good on a hybrid turbo.

So saying "I run 27psi" is actually an extremely broad statement.

With the right fuel.... I don't see 29psi as an issue on the right hybrid.

 

[Hijinx]

Nothing wrong with that at all. But again, peaks are not as important as what it's running on the top end.

I maxed out my map sensor on a regular bases on my OG cyborg ( 29.4psi ) and held 26-27psi to redline to make 290whp. With the cyborg39 I expect about the same but making more power of course.

Just realize that 27psi at 3600rpm is a HUGE difference compared to 27psi at 6500rpm. So when you say "I run 30psi" that could be perfectly fine at 3600rpm. While the same "I run 30psi" at 6500rpm is not good on a hybrid turbo.

So saying "I run 27psi" is actually an extremely broad statement.

With the right fuel.... I don't see 29psi as an issue on the right hybrid.

I run 33-34psi. But, that's only here, not there. But seriously, OP, SS is right.


Some Guy On The Internet

 

[Brickell FIST]

SS thanks for the breakdown, much appreciated.