Valve timing effects on spool time, geeting quick spool

[3literpwr]

Hey guys im new to the board, but have recently built a 2.0 awd talon
for open class scca rally....... I have a fully balanced and blue printed motor thats ported here and there and what have you.... its got 8.3:1 pistons and eagle rod, no balance shafts, evo 3 big16 and all that jazz.

My question is does anyone know how much valve time on these car effects spool time?

When I was building the motor some one told me to retard the exahust cam one tooth to build some more power, but I cant rev the car too high because I need to run a 40mm restrictor in the turbo per class rules...


Any ideas about quicking the spool time WITH OUT using anti-lag

 

[Suparata]

Gentlemen ,
We have here a real enthusiast who dared to do something else than almost everybody else by choosing Rally over other so called " Competitions" and nobody is willing to help this guy out. Isn't it funny that every time something silly is posted a lot of people jump on the thread but when a guy that did not get afraid of the cost of doing something more expensive than most will ever do, nobody has anything to say about it.
Now to your question valves timing play a big role in what happens and when it happens . Retarding the exhaust cam one tooth will move your powerband higher but what you really need is a set of Adjustable Cam Gears and play with them to get the power where you need it. I now you would like to have full boost at 1500RPM if possible but that's not going to happen . Don't forget that the restriction you have can help you get nice Torque out of your engine. When you will get the desired setup get ready for the race that follows: you will be tweaking things again.
Good Luck in what you chose to do. I'm sure it will give you great satisfaction and a lot of white hair too.

 

[kpt4321]

Originally posted by Suparata
Don't forget that the restriction you have can help you get nice Torque out of your engine.

The restriction doesn't help you get more torque.

As far as I know, changing the cam timing won't make much of a difference in terms of how quickly boost builds, but it will move the powerband around such that you can get more power at lower rpm's, which will feel like quicker boost.

 

[3literpwr]

Thanks for the tips guy, but from what I have heard is that the restrictor speeds air into the motor and helps make some extra torque in the lower r's...... If this is true I am unsure but I will have a answer soon after I do a bit of tuning on the dyno......

Currently the my 3rd restrictor design flowed 480cfm@ 28" 0f H2o(14.7) on my uncle flow bench.........

On another note I have decided to work with a cam guy down in tennesee about making some restricted motor specific cams.......
The kind that only make power to 6k....... This should help with lag and such.......

Thanks again

Larry Parker
#622 SCCA club rally

 

[Suparata]

Originally posted by kpt4321
The restriction doesn't help you get more torque.

As far as I know, changing the cam timing won't make much of a difference in terms of how quickly boost builds, but it will move the powerband around such that you can get more power at lower rpm's, which will feel like quicker boost.

WRC cars have a 34mm restrictors and they crank out 300HP and 410-440 ft lb of torque. I am sure it is not only because of the restriction but it sure plays a role in this.

 

[kpt4321]

Originally posted by Suparata
WRC cars have a 34mm restrictors and they crank out 300HP and 410-440 ft lb of torque. I am sure it is not only because of the restriction but it sure plays a role in this.

They don't make a lot of torque because of the restrictor, their horsepower output just sucks because of it. If you were to remove the restrictor, the torque output would not increase a lot, but the power would go up to well above 600 horsepower.

This is because horsepower is determined by total airflow, which a restrictor places a limit on. Torque is determined by airflow per revolution, which you can achieve without huge total airflow numbers.

 

[RallyGSX]

I am building a rally car as well, and think you may be over thinking the low end thing a little. As mentioned before, a WRC car has a 34mm restrictor, SCCA's 40mm has %28 more area to flow through. A WRC car routinely revs to 7000 RPM, sometimes beyond. This is well within the range of, say, HKS 264 cams. It seems easy to keep the car in the 4-7000 RPM range all the time.

Also, why the BIG 16g? It is a bit more ineffecient than the small 16g, you are trading minimal top end gain (that you will never see w/ the restrictor) for loss of lower range power and slower spool... I want a L1R, saving my $$$

I have heard a restrictor will put torque lower in the RPM band as well, not sure why.

 

[RallyGSX]

I was thinking about restrictor function, and was unable to find if WRC cars have the restrictors placed upstream or downstream of the turbo.

The argument that a restriction produces more torque lower in the rev range would only make sense to me if it was placed near the throttle body. A restriction placed within 50mm of the turbo inlet (upstream of the turbo) seems like it would only limit the amount of air the turbo's compressor wheel could process, and limit the efficiancy of turbo's compressor section. The effect would be a lower boost level the turbo could produce before just heating up the intake charge.

I have heard on Speed TV that the Mitsubishi EVO rally cars produce 440 HP, not sure if thats WHP or not.

Anyone have any facts or thoughts on this matter?

Thanks,
Dave