What other mods can i do...?

[kinkyllama]

If you made 200Whp at 2300RPM and kept that all the way to redline.... that would be ideal.

I know what you mean.. im not focusing on peak power.. but i dont know how to gain power throughout the powerband other than hurting higher rpm power. I only need enough power at 2300rpms to drive on city streets. On the track i dont drop below like 4k rpms (maybe less.. i dont wanna plug all the info in right now). So making power below that is usless...cept city driving where i dont need much power.

[kinkyllama]

My personal opinion is that water isn't the best "cooler" for you...... I'd go with a compressed gas such as CO2, compressed air or Nitrous.

With a gas system you can't be disqualified...... water is however grounds for getting kicked off the track.

CO2 and Compressed air are cheap..... when the gas is released from the pressurized canister it comes out very cold..... I can't remember exactly but I think it's around -65 degrees.... so it's possible to have colder air entering the intake than the that of the ambient air temperature.

Some Air/Water hybrid intercoolers use a presurized gas to cool the water which then cools the air going into the intake.... these intercoolers can have a thermal efficency higher than 100% (due to the fact that it cools the air below ambient air temp)

Cant have anything compressed on the track...otherwise id look down those roads.

[kinkyllama]

How can i upgrade the ignition though?

The basic upgrade would be to add one of my "driver" circuits and run an MSD ignition box like the DIS-2.

Yeah.. but thats the only option i have w/ our ignition systems, right? I thought you had none left for the time being and ive just been waiting for you to make more

[Audacity Racing]

her erfinder... correct me if i'm wrong... but don't smaller valves lead to bigger horsepower? i mean, that's the point of multi-valve heads like ours... to make smaller valves that generate less resistance to air going into the engine. it also makes for smaller parts, thus less individual interia which in the end results in less valve float...

i'm right aren't i?

[PrecisionBoost]

smaller valves lead to higher velocity which makes for a more turbulant and better burning air/fuel.

Less resitance.... larger ports....larger valves make more power at higher RPM..... but power in the lower RPM is significantly less ( think honda engine)

medium resistance.... small ports.... small valves make more power at lower rpm levels but power at higher RPM levels is significantly less

[Audacity Racing]

why is it then that the 4 valve ford engines make way way way more hp than the 2 valve engines?


it doesn't make sense that a large valve would offer better performance at the top of the rpm band.


a specific example would be the 2005 ford expedition. the added anotehr small valve instead of two larger ones (which equal the same flow rate comparatively) yet if boasts 8 more hp over the other model. also, on our formula sae car, we used a briggs and stratton head that we set-up with large valves, and with small valves and got significantly greater hp ratings (112 big valve, 137 small valve)


another thing would be runner length to power ratio. the higher the rpm, the shorter the runner to create the best power (think vgis).



it seems contradictory that smaller valves would promote better combustion but limit hp...

[Audacity Racing]

ok... i got it figured out....


it's all relative to bore/stroke, piston sweep vs intake volume (volumetric efficiency, and port design.


apparently ve is really all that changes unless you make HUGe changes to a head's valves. my ve was rated at 98% as is, so i'm not worried about how i changed it with teh smaller valves... i'm happy with that anyway.

[PrecisionBoost]

Ok....I'm going to lay out something of a concept...

Lets say you set up the car to make 200Whp at 10psi of boost

Here is a guess at the stock powerband....
75whp at 2500 RPM
120whp at 3000RPM
180whp at 4000RPM
200whp at 5200RPM
195whp at 5700RPM

If you enlarge your ports this is what you will get with 10psi of boost

50whp at 2500 RPM
100whp at 3000 RPM
180whp at 4000 RPM
200whp at 5200 RPM
220whp at 5700 RPM

Thats great.... but you are limiting your car to 200WHP so you have to turn down the boost to 8psi to keep your peak horepowe down....

50whp at 2500RPM
88whp at 3000RPM
150whp at 4000RPM
180whp at 5200RPM
200whp at 5700RPM

So..... if you compare that to stock.... it sucks.... your car would be slower.

Sure you make 200WHP on less boost..... but that also means your powerband is not as good.

Now..... if you decreased the size of the ports......yes..... restrict port size so that it's smaller than factory.

At 10psi of boost your power band would be...

90whp at 2500 RPM
130whp at 3000RPM
160whp at 4000RPM
170whp at 5200RPM
150whp at 5700RPM

Now.... you might say this sucks.... but you just need to bump the boost to 12psi

Now at 12psi your making...

90whp at 2500RPM
135whp at 3000RPM
195whp at 4000RPM
200whp at 5200RPM
190whp at 5700RPM

So.... large port vs small port...... you had to increase the boost from 8psi to 12psi to make the same peak power.

So.... the volumetric efficency of the larger ports is better.

But...... a turbo cancels out any increases in volumetric efficency by simply adding more boost.

Compare the restricted power band versus large port power band.

90whp at 2500RPM................50whp at 2500RPM
135whp at 3000RPM..............88whp at 3000RPM
195whp at 4000RPM..............150whp at 4000RPM
200whp at 5200RPM..............180whp at 5200RPM
190whp at 5700RPM..............200whp at 5700RPM

So at mid rpm.... 4000RPM.... your restricted port head is making 45whp more than the large port!!!!

Hopefully you understand what I'm talking about and why you shouldn't port your cylinder head.

Sure it is more efficent.... and you make more power at a given amount of boost..... but you sacrifice low and mid power to get it.

Given you have a turbo.... you can simply make up for less efficency with more boost.

[Audacity Racing]

yeah... i answered my own question


(and i'm running 20 psi)







i'm still confused as to how my hp was so much higher by just raising compression a little bit and makeing valve size smaller (based on my work with the fsae car). i know i'm revving significantly higher and making hp higher... so how does that work?




i'm not concerned with how it all works though because i'm a fully built engine (or will be) pushing way more boost and not limiting myself. the valve issue comes into play when you do as you did by limiting the hp to a certain level. if going for max power, i've set myself up right.


thanks for the info

[PrecisionBoost]

These numbers are just simple guesses based upon knowledge of engine design.... they are by no means correct..... it's just a theory.

Now.... having said that.... I have been thinking about what daewooluvr said about compressor surge.

I think this is definitly an issue.... the more restriciton the larger the posibility of compressor surge..... so if you turbo is a little on the big side you will need larger ports to decrease flow resistance.

If your turbo is just right.... you should be able to do what ever you want.

Also..... running 8psi will create less compression heat than 12psi due to a better volumetric efficency.

Less heat decreases the likelyhood of detonation.

So.... it's a mixed bag.... more restriction creates better port velocity which creates better power at low and mid RPM levels..... you need more boost to get peak horsepower and you create more heat.

less restriction makes the car run like crap in the low and mid rpm band but it makes the engine far more efficent at higher RPM levels so less boost is required to make peak horsepower and you create less heat.

Basicly..... the only way to really know is to fool around with several different cylinder heads.... one stock....one mildly ported....one ported so large you could fit your hand in there

[PrecisionBoost]

Two smaller valves have more "port volume" than one large valve.

So 8V engines make better power down low due to higher port velocity and 16V make better power up high where they flow better than the 8V

8V have better volumetric efficency at lower RPM and 16V have better Volumetric efficency at higher RPM

The best design is one where one of the two valve in a 16V stays shut until 3500RPM.... then the extra valve opens up.

This gives good 8V VE down low and good VE up high..... several manufacturers are starting to use this design to increase power down low on 16V engines..... which gives better fuel economy and better emissions.

[PrecisionBoost]

Smaller port makes the air flow through faster...... just like a garden hose with your thumb over the end.

Turn on the water 10%.... put your thumb over the hose to make the exit port smaller....the result is a fast jet of water due to the fact that the exit hole is small. ( high port velocity)

Then take off your thumb.... the water dribbles out the end of the hose very slowly (low port velocity )

Turn the water on 50% and put your thumb over the hose..... you still get a huge jet of powerfull water.... but your restricting how much flow is occuring. (high port velocity with some flow restriction)

Take your thumb off.... and you have a decent stream of water coming out..... nothing spectacular like the water jet but the flow is decent and the velocity is decent

Next .... open up the water 100%..... with your thumb over the top your jet is the same as it was at 50% (or slightly stronger) but you feel a huge restriction as the water is trying to push your thumb off the end of the hose.

Take your finger off and wham.... you get way more water flowing out and a really decent jet....perhaps even as much as you had with your thumb over the hose at 50%


So...... thats a simple explaination of port velocity vs resistance

You need the air to flow fast enough to burn correctly but with the least resistance possible..... current stock ports are a comprimise between the two in order to ensure your car runs smooth and makes good power at lower RPM levels while making maximum power up at higher RPM.

[PrecisionBoost]

Sorry to get so off topic..... perhaps I should move this..... let me know if you want me to.

[kinkyllama]

Sorry to get so off topic..... perhaps I should move this..... let me know if you want me to.

No its fine.. i like reading it and learning more anyways.

I dont care about power at low rpms.. but mid to high is very important. I never hit low rpms other than the street, which i stay under 3k rpms. On the track i never drop belove 4100rpms unless im doing auto-x then i never drop below 3700rpms. So as long as im making as much hp in the normal driving rpm range w/ the turbo as im making now.. ill be happy

[MMamdouh]

smaller valves lead to higher velocity which makes for a more turbulant and better burning air/fuel.

Less resitance.... larger ports....larger valves make more power at higher RPM..... but power in the lower RPM is significantly less ( think honda engine)

medium resistance.... small ports.... small valves make more power at lower rpm levels but power at higher RPM levels is significantly less

reminds me about the 1.5 SOHC vs. 1.6 DOHC OPEl engines... both pumped out 101 HP but the SOHC got almost the same torque no. at 600 RPM less than the DOHC.

MMamdouh