restrictor plate vs power output

[mike d]

recently ive been toying around with the idea of differnt drivetrain options, however the one X factor is the effect of the 20mm hole alowwed in the restrictor plate,,

simply put, how much power are peaple gennerally producing on a 550cc+ moter with the restrictor plate? how does this compare to what the moter would produce without it?

best wishs
mike d

[Ian M]

Most teams are probably around 65-70hp with the restrictor on the 600cc inlines, whereas these engines would make 100-105hp stock.

[Mike Hart]

I'd agree with Ian. Around 65-70 is a realistic aim with a tuned intake and exhaust and anything up to around 80-90bhp if you go crazy on the engine tuning side. Graz impressively proved 95bhp or thereabouts on the dyno in Germany. I'm not entirely sure what they'd done, but a variable intake and some new cams were part of their work I believe. The key is finding power using all the abilities of whatever ECU you run. Just adjusting little things like injector firing angle and making percentage changes for each cylinder can find you a few bhp and it all adds up!

[TMichaels]

The normal values I saw on the dyno in germany was between 78 and 84 bhp for four cylinder 600cc unmodified engines. We also developed 83.5 bhp with our Suzuki GSXR-600 K4. Calculating with the maximum possible airflow, you end up with a maximum of around 93bhp. The 95bhp, or whatever it was, of Graz are only a calibration problem of the dyno. It is easy to develop around 90 bhp with modified cams. But I don't know why everybody is worrying about top end power. Only the usable torque over rpm counts, in my opinion.

[mtg]

I don't think you'd make much power with a restrictor plate.

Mike D: notice in the rules it does not say your restrictor has to be a plate, and I've never seen anybody run a plate with a hole in it. Everybody runs some sort of venturi styled restrictor.

And the 4 cylinder 600 supersports stock (depending on which one you use) usually put down 90-110 hp at the rear wheel of the motorcycle, which will have similar drivetrain losses as most FSAE cars.

[exFSAE]

I would think dyno variability testing an engine of this size would make car-to-car comparisons silly unless they're all on the same rig.

Hell this is true of any car, no?

Easiest way to pick up 10hp.. go to a different dyno.

[Welfares]

The exhaust i built seemed to magically loose us about 15 HP, it is in fact WORSE, than the log plenum type manifold we built for an experiment. But, as you say, different dyno.

This is my first year tuning the engine solo, when asked for advice it was pointed out to me that "perhaps the problem exists between the control panel and the chair."

[Wesley]

PEBCPAC instead of the usual PEBKAC?

Yeah, most dyno's are only useful as a comparative, not quantitative tool - hence why you don't get points in FSAE for dyno numbers. It's a tuning tool, from which you can make marginal improvements between runs.

Like my dad always said, show me your times or stop wasting mine.

As for running a restrictor plate, like was suggested, that will leave a lot of power on the table. The rules on the restrictor only specify diameter.

If you can fold a hypersphere induction orifice into that 20mm that draws from the 4th dimension... then you shouldn't be in college.

[BeaverGuy]

Originally posted by Wesley:
If you can fold a hypersphere induction orifice into that 20mm that draws from the 4th dimension... then you shouldn't be in college.

But aren't those the people that never leave
college?

[Wesley]

I suppose thats true. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif