max HP on stock compression?

[elwesso]

Have we ever come up with the conclusion on the highest HP you can go on stock compression (10.2:1)?

Ive heard varying figures but it might be worth discussing... On either race gas or pump gas......

[Q45tech]

That depends on the rpm where you measure HP and the peak BMEP........10.2 CR static is not the running CR.

[sinfiniti]

As a general rule its a guess to punt on 110Nm/L so if this (max) torque can be lifted to about 5000rpm you would see 376lbft at 5000 which equates to ~360hp or 268kW (obviously at the engine)however if you could raise the rpm that this torque is developed at (say to 5500) you could develop 390hp or 291kW. But then you would be hindered by the flow restricion of the plenum design, an dspending money on this (custom plenum) would be a waste of money ie: law of deminishing return etc...

Raise the comp ratio, go with bigger cams custom exhaust (obviously) custom inlet manifold etc and you could probably push the 120Nm/L mark at say 6000 with 90% of peak torque available at 7000 and 80% still there at 8000 (90% is 486Nm, 80% is 432Nm)

100% 540Nm @ 6000 = 464hp or 346kW 90% 486Nm @ 7000 = 487hp or 363kW 80% 432Nm @ 8000 = 495hp or 370kW

....but this is approaching full house race engine... so not practical

[sijoko]

Have we ever come up with the conclusion on the highest HP you can go on stock compression (10.2:1)?

Ive heard varying figures but it might be worth discussing... On either race gas or pump gas......

Are we talking N/A or Forced Induction?

[elwesso]

Id say with boost.

[sijoko]

Id say with boost.

Detonation is what will limit horsepower on any engine, whether a stock 10.2 CR unit or a built for boost 8.5 CR version. If you tune it properly and use high octane, you can push it to 8-10 psi on a stock engine which will net over 450 hp.

[Mettler]

I'd be careful about running more than 5-7psi until you'd got the tuning sorted.

[ScottJackson]

On nitromethane mix with a big ice box intercooler, A LOT. Keep it well out of detonation and I bet a person could make well over 1000hp for a while with a stock VH45. I mean, if the thin webbed, 2 bolt main, stock 5.0 mustang guys can make 600hp at the crank before the block splits (on cast crank and cast pistons, also at likely lower rpm than the VH), I don't think 1000hp is out of the question with a stock VH45 on boost.

[Mettler]

That's a pretty extreme case though isn't it?

It would be nicer figuring it out in terms of a reliable street setup on pump gas.

[elwesso]

The thing I wonder about is if at a certain boost level, assuming a stellar tune, on pump gas, are we gonna run out of fuel first (by injectors) or are we going to detonate first? The quesiton is, is it worth upgrading to 555cc injectors on an otherwise stock VH45 or are we gonna detonate with the 370s before we run out of fuel...?

What do we calculate that the 370s are good for on a VH45? Ive never been sure how to calculate that...

If we could dump fuel from some 555s and see maybe 600HP at 15lbs of boost thatd be sexy.

[Mettler]

I'm sure there are spreadsheets available to calculate that... I haven't got any information like that handy yet, I'm not on to tuning just yet.

[mtcookson]

http://www.rceng.com/technical.htm#WORKSHEET

I think its a little on the conservative side but using 43 psi, 80% duty cycle, and a BSFC of .65 (just to see the limits), it comes out to right under 350 bhp. Fuel pressure can be turned up and the BSFC is likely lower than that.

Take the VG30ET for instance. Guys are pushing 420's well over 400 whp before maxing them out. Not sure at what pressure but the duty cycle is likely no more than 80% (I think that's where the ecu caps it). Say if they were running 80% duty cycle at 60 psi aiming for 450 bhp, that would be a BSFC of ~.50.

You can mess around with that thing and get some ideas. Like I said above, I think the ratings are definitely conservative.

I think you're right on the 555's though. Just as comparison, I think most Z32 guys run the 555's up to around 500 hp. With a couple more injectors in the engine, it can be more than that. Basically, I would say 600 hp with 555's would be cake in the VH.... I think its time for me to go to bed.

[elwesso]

Hers the question of the day.

Lets assume we have some sort of injector that can put out enough fuel for 700HP at 80% D/C. DO you think its possible to get say 500-600HP on pump gas out of a stock compression VH45? We're assuming a good tune and the air is nicely intercooled (but nothing beyond a decent FMIC). The bottom line is, where do we have to draw the line (at what HP on pump gas) where adding more fuel does nothing to stop detonation?

We're going very streetable, nothing extreme as far as the parts are concerned. no racey icebox intercooler, all parts would be on a streetable car.

[darinz]

My truck will be on the dyno within a couple of weeks. I'm still running 370 injectors but will be running avgas. We are hoping to get 10psi but it will all depend on what happens. We just want to see what we can do with the standard injectors before spending more on new injectors. (with adjustable fuel pressure) This motor won't be getting decompressed at all reguardless of the out come as we don't want any bottom end loss.

[Mettler]

darinz: even if you decompressed the motor, running a couple of smaller turbos (think factory S15 turbos) you'd have power from 2000rpm or so onwards.

[mtcookson]

Hers the question of the day.

Lets assume we have some sort of injector that can put out enough fuel for 700HP at 80% D/C. DO you think its possible to get say 500-600HP on pump gas out of a stock compression VH45? We're assuming a good tune and the air is nicely intercooled (but nothing beyond a decent FMIC). The bottom line is, where do we have to draw the line (at what HP on pump gas) where adding more fuel does nothing to stop detonation?

We're going very streetable, nothing extreme as far as the parts are concerned. no racey icebox intercooler, all parts would be on a streetable car.

I think Slim was estimating 500-600 hp on his setup and I don't believe he's using anything more than pump gas... I'm not sure though. I bet the VH could handle that pretty easily though.

[elwesso]

I realize what slim estimates but honestly (knowing he probably wont see this) I think thats pretty optimistic.. Hes running stock actuators so thats like 10 lbs, i dont think he said he actually sees 8lbs. I think that its got so much torque over a super wide powerband that it feels like a lot more than it is. Plus the JWT boost chip makes the car run super rich.

Is there any way to predict detonation somehow using caluclations or is it only a trial/error sort of thing. im sure you could calculate somethign but whether or not it would easily translate to reality is another thing.

[mtcookson]

I think he only said he was running 5-6 lbs. of boost actually. But you're probably right though.

As far predicting detonation... I would think that would be very hard to do. For most, its definitely a trial and error thing.