What determines the limit of cylinder pressure?

[Jared_80]

What is the limiting factor in increasing boost pressure? Is it the temp, is it the thickness of cylinder walls, or is it the fuels resistance to detonation? I remember reading about a Lotus race car runing over 100psi of boost. What made that engine so different from the high strength turbo blocks that we have today? If all temp problems could be controled with the addition of some kind of direct port water injection what would there be a limiting factor other than the strength of the rotating assembly and block?

[ivymike1031]

did you want to know about increasing boost pressure or increasing cylinder pressure? They're not the same...

[MustangRoadRacer]

1. what ivy mike said
2. direct port water injection is crap
3. the limiting factor is tied into all of what you said.
Increasing boost increases temperature, which, in addition to pressure causes detonation if the fuel has a low octane rating, which damages the internals of an egine (rotating assembly and block).

[454Casull]

Water injection does let you use more boost.

[kfoote]

Adding to the list of potential limiting factors:
Head gasket material/strength
Cyllinder wall thickness/strength
imporities in the valve seat/valve surface
Piston ring strength

Basically, it depends on the engine and what has been done to it. The highest boost I know of that was reliable was 120 PSI in the 1993 Toyota GTP engine. They managed to get 1200 HP out of a 2.2L engine that won the 24 hours of Daytona.

[pod]

Originally Posted by kfoote

Adding to the list of potential limiting factors:
Head gasket material/strength
Cyllinder wall thickness/strength
imporities in the valve seat/valve surface
Piston ring strength

Basically, it depends on the engine and what has been done to it. The highest boost I know of that was reliable was 120 PSI in the 1993 Toyota GTP engine. They managed to get 1200 HP out of a 2.2L engine that won the 24 hours of Daytona.

wtf

[SaabJohan]

Originally Posted by kfoote

Adding to the list of potential limiting factors:
Head gasket material/strength
Cyllinder wall thickness/strength
imporities in the valve seat/valve surface
Piston ring strength

Basically, it depends on the engine and what has been done to it. The highest boost I know of that was reliable was 120 PSI in the 1993 Toyota GTP engine. They managed to get 1200 HP out of a 2.2L engine that won the 24 hours of Daytona.

120 PSI is hardly the boost pressure since single stage turbines can't get enough power for this kind of boost. The highest boost pressures used in racing as I know of is 4.5 bar in the old F1 engines.

The 1200 hp Toyota engine has probably a boost of around 3-3.5 bar.

[Sluttypatton]

You mean the old Toluene fueled F1 engines right?

[SaabJohan]

Originally Posted by Sluttypatton

You mean the old Toluene fueled F1 engines right?

Yes.

Their fuel was toluene based but contained some even nastier stuff. The fuel was the biggest reason for the increased power output (and therefore increased cylinder pressure). The synthetic fuel could however cost as much as $300 per liter but was 60% more dense than normal gasoline and contained a lot more energy.

[Neutrino]

i believe that they used toluene in old F1 turbo engines because of its particularly good knock resitance

[kfoote]

http://www.allamericanracers.com/eagl_mkIII_gtp.html

That's got the specs, and I apologize, the car was de-tuned for the 1992 and 1993 seasons due to air restrictors limiting the boost pressure. These engines did not have head gaskets, and I believe at their most powerful, they were some form of multi-stage turbocharger. This car still holds the track record at Lime Rock (with the chicaine it lapped faster than any other car has without the chicaine). The rules that this engine was originally built to were not as restrictive as the mid-80's F1 engines (which did have more power and less displacement), with a few additional years of R&D. This was Toyota's biggest factory involvement at the time and they put a LOT of money into it.

I believe the cars at the time had to run a spec methanol fuel, but I'm not 100% sure of that.

[SaabJohan]

Originally Posted by Neutrino

i believe that they used toluene in old F1 turbo engines because of its particularly good knock resitance

Not only knock resistance, energy content and density was very important since they were limited to a maximum volume of fuel for the races.

Some of the contents are said to be aniline, coumarine, cresol, cumene and naphthaline.

[SaabJohan]

Originally Posted by kfoote

http://www.allamericanracers.com/eagl_mkIII_gtp.html

That's got the specs, and I apologize, the car was de-tuned for the 1992 and 1993 seasons due to air restrictors limiting the boost pressure. These engines did not have head gaskets, and I believe at their most powerful, they were some form of multi-stage turbocharger. This car still holds the track record at Lime Rock (with the chicaine it lapped faster than any other car has without the chicaine). The rules that this engine was originally built to were not as restrictive as the mid-80's F1 engines (which did have more power and less displacement), with a few additional years of R&D. This was Toyota's biggest factory involvement at the time and they put a LOT of money into it.

I believe the cars at the time had to run a spec methanol fuel, but I'm not 100% sure of that.

It used a single, quite large turbocharger. I believe the engine was also used in TOMS Toyota LMP and Rod Millens Pikes Peak cars.

The Eagle was infact constructed very cheap, they even used vacuum bags instead af an autoclave since they didn't had any.

The power output was 750 hp in 1992 and 700 hp in 1993.

The biggest reason for its success was probably the aerodynamics, the use of a front diffusor.

The use of no head gaskets is also used in F1, the head and block is polished to a very high finish so they will seal without a gasket.

[kfoote]

Originally Posted by SaabJohan

It used a single, quite large turbocharger. I believe the engine was also used in TOMS Toyota LMP and Rod Millens Pikes Peak cars.

I'm not sure about the TOMS Toyota LMP, but the engine was used (unrestricted) in a couple of Rod Millen's Pikes Peak cars (and a Pikes Peak Toyota Tacoma as well, I believe)

[Jared_80]

Originally Posted by 454Casull

Water injection does let you use more boost.

Read the book Turbocharging. They point out that a water injected engine can run 70% higher pre-ignition pressure without knocking. That is more boost pressure in my book.