Boost pressures

[R8VXF]

Just wondering what boost pressures people have been able to run their engines up to? I understand that you start to run into cooling issues with roots style, so would going centri and a FMIC allow higher boost pressures due to the better cooling abilities and what theoretically could these engines handle? (Obviously other components would have to be upgraded...)

I know that the LSA runs 9psi standard and have seen that changing the pulleys can get you around 13psi due to I guess hitting the cooling limitation of the stock s/c.

My dirty derv runs 21psi boost from the turbo, but part of that is also down to the piston design allowing for higher pressures. Would 21psi be feasible in a daily driven petrol?

[ArnieVXR]

17.5psi was 1206hp for me. I have run into the mid-20s, so it can be done. I'm guessing that I could probably make 30-psi on pump gas. You're talking about a decent four figure hp output. What are you hoping to achieve?

As for the engine, you'll be needing an LSX based motor for longevity. Heads are known to lift with the stock head bolt pattern. I'd suggest an LSX376-B15 would be a good start, though this is only rated to 15psi (seems a bit conservative to me TBH).

As for daily driver, you really won't be using that sort of power on the public highway. I'd say mid-700hp is the maximum for a regular drive that can actually be used and enjoyed.

[R8VXF]

Nice one. Not really planning on much, just more of a thinking out loud/dreaming type thing. What s/c were you using to get those boost pressures?

[ArnieVXR]

The type that looks like a pair of turbos

Can't believe I've found someone I haven't bored with my build thread...

[R8VXF]

Haha, will go hunt for it in a minute, should be a nice read

There is so many different ways to mod these engines, I am just getting my head round all the different options and what they can actually handle. Can't wait to take delivery of the GTS, hopefully less than a month to go

[anonymous-user]

Mine runs about 14psi but rather than looking at boost, think about air flow and blower RPM instead. A TVS blower will become a heat pump if you go too far (ask me how I know) so you are better off sticking in a decent cam, sticking on a slightly smaller pulley and calling it a day. If you want to go nuts, you'll need turbos or big centri

[ARAF]

R8VXF said:

My dirty derv runs 21psi boost from the turbo, but part of that is also down to the piston design allowing for higher pressures. Would 21psi be feasible in a daily driven petrol?

Using your dirty derv as an example, anything is possible, if you build the engine for that reason, and this is what some here have been on about - though one or two have made FI sound like it's the spawn of the devil.

Big boost on a big capacity will start to get laggy through a lower compression ratio though, won't it?

[R8VXF]

What got me thinking about boost pressures was the whole FI v NA thing, with people saying that the limit is the s/c due to the heating issues. This got me thinking about a centri as you can put in a nice large FMIC which then got me wondering what the boost pressure limit was after finding out the derv boosts at 21psi. Random chain of thought I know

But yeah, prob will just change the pulleys/cam for starters, then maybe in a year or two go for a Heartbeat SC or a centri if I can afford the time/money to do it.

[ArnieVXR]

The TVS1900 in your new car is plenty good enough for 700+ horsepower, which is all you want in a road car. A TVS2300 won't give you much more, so really isn't worth the extra.

Centris deliver power in an entirely different way. Boost rises with revs, so max power is up high in the rev range. It'll take some getting used to after you've had a PD supercharger. Centris of a size big enough to eclipse a well sorted TVS are very big and the gearboxes are very noisey in a screeching sort of way.

Take wormus' advice on this one.

Edited by ArnieVXR on Tuesday 18th November 21:57

[R8VXF]

As I said, it is more of a pie in the sky/thinking out loud type of thing. Knowing me I will never get round to doing anything on the car anyway, I just like to understand what is possible and how all these new components (new to me anyway) work and interact with each other

[stevieturbo]

R8VXF said:

Just wondering what boost pressures people have been able to run their engines up to? I understand that you start to run into cooling issues with roots style, so would going centri and a FMIC allow higher boost pressures due to the better cooling abilities and what theoretically could these engines handle? (Obviously other components would have to be upgraded...)

I know that the LSA runs 9psi standard and have seen that changing the pulleys can get you around 13psi due to I guess hitting the cooling limitation of the stock s/c.

My dirty derv runs 21psi boost from the turbo, but part of that is also down to the piston design allowing for higher pressures. Would 21psi be feasible in a daily driven petrol?

You're trying to compare apples to elephants.

Boost is not all the same, so wrong to use a boost target as any sort of goal.

But yes you could very easily run 21psi all day long as a daily driver. But you'll either crash, lose your license or destroy lots of tyres in the process.
That's after you build an engine package to be reliable doing so.

Even the crappiest LS engine pushing 21psi from almost any boost source will make a lot of power and be rather impractical to actually use that power on the street.

[minime68]

With the LSA you should be fine at around 13psi. Most run that and call it a day. If you want to really push it then you can venture into the 15-16psi+ range and then you would have to worry about heat and pistons. Of course, you will see less boost if you port the blower or get headers but still make more power.