Pro Stock John

iTrader: (34)

In my experience, you can still hook 600rwhp (low to mid 10's) on drag radials with some pedaling. Now put that car on a 28 slick or a big drag radial and it hooks okay. Once I got this this mid 9 second level, the car goes sideways for a whole block even with a 28W at 11 psi.

cablebandit

iTrader: (37)

question is what tires is he running on the street....

Websy21

iTrader: (34)

well for me I have M/T's 315 street et's

cablebandit

iTrader: (37)

low comp for you then and hit the boost!!!!!!!!

Rudolph

iTrader: (1)

So, the conlcusion is....

Low boost, high comp!! High boost, low comp! ? Just getting my thoughts clear.

The static comp ratio on my ride is 10.5, but I am planning to go with a Maggie SC which is going to be on the 7 psig limit for my setup!! What would you say on the this? (cam 232 240 .595 .608 115 LSA) Is this Comp ratio friendly a setups such as the one I am planning?

MIGHTYMOUSE

iTrader: (59)

higher compression would be great for driveability and mileage, but i would just be too scared of a bad tank of gas or a hot day etc. etc. to be totally comfortable wacking on it.


the hi comp craze i think is for class racing where other things are limited like turbo size, cubes ect.. not octane

Rudolph

iTrader: (1)

I guess that when you have a ride with the setup your car is equiped with is something to worry about, something extreme

But when you are going with low boost such as 6 psig and CR 10.1, guess there would not be much a problem!! Well, that is a thought! Based on you ride, I guess that you could know much more than I do

Websy21

iTrader: (34)

Yes Mickey Mouse, I mean Might Mouse is da man. Well one of the highly knowledgable gentleman on here willing to reveal his expertise thoughts When it boils down to it, I do really agree on the reasoning behind the lower compression in which I will probably go. Would be nice to have the benefits of the higher CR but oh well, power should suffice my needs.

Say out of curiosity to the guru's, what one one yield on average for a gain in milleage from a gain of one point in CR? Would it really be that much, I know the power level would be quite significantly different. Probably more so in a boosted application too.

bifster

well guys seems like this topic has taken off sorry i havent replied for a while... but ya mighty mose thanks for the info and i totally understand your concerns about fuel consistancy. i never tend to drive far enough with the car that i cant make it back home to the new sunoco that carries 94... and we have about 7 local shops that carry race fuel so octane really isnt muc of a problem.....
one question i had tho was for mighty... ive heard tons of good stuff about you and your build but i have never heard anythign about your numbers like CR or boost levels i dont know if you want that getting out but i was just reading in another thread you are using the new felpro head gaskets too. either way i wouldnt mind picking your brain a bit about set up as I like the idea of high compression and boost on the street. I will be running et streets all the time and a good set of MT 28"x12.5" on the track rinckle walls. So maybe that will give ou guys some more info and guidnce as to the set up.

bifster

sorry i forgot to mention mighty mouse I know your torque gragh there in your sig but I like to know the math behing the motor haha thanks

MIGHTYMOUSE

iTrader: (59)

to me the whole idea of a built motor is to make more hp than you had before.

setting up same compression as stock will get you same horsepower on pump gas as stock... it just means that it will take more of a beating without breaking a piston like stock does.

i personally wanted more than that on the same gas so to do that you gotta drop compression.

i dunno how much worse my mileage is because of the compression, or because of the cubes, or because of the gear, or the stall, the injectors, or my cruise a/f, but collectively i run just under 20 highway... and it gets me around in traffic just like any other commuter car would.

you could say its a little soggy on the bottom... is that again because of the compression or maybe the big turbo... who knows but at the same time i dont see anyone beating me off the stoplight and me pissed beating on the steering wheel blaming my compression...

same at the gas pump normally im out of gas because i floor it a lot not because of the compression.

my compression was originally around 8.0 but i have had the heads surfaced since the original calculation.. i would say between 8 and 8.2 still. in the interest of longevity, i do not allow myself to run more than 15# pump gas only, no more than 17-18 on pump gas and methanol, and i have yet to run more than 23# (dyno) on race gas and meth

my best track time is at 17.3# peak on 17" drag radials which is where i run it on pump gas and meth, same as it is set to all the time daily driving. I mix in 112 at the track but do not touch the tune.. its just for insurance. at 17# i'm at about 17* timing

if you want more throttle response get a supercharger.

bifster

very understanding mighty. Im not sure of your build tho r you using anything in the motor IE forged crank and pistons rods? and cubes ? your obviously making good power around 17 psi seeing asa how your in the quest to low 9's but is that with 1000hp? looking at that torque grapg or am i miss lead?? either way i believe with a 427 build ay hopefully 9:1 i can run some decent numbers with 10 psi on the street and up to 15 on the track not sure yet but tunning is fun so ill have multiple tunes with me in the car on the computer ready for anything.

Pro Stock John

iTrader: (34)

A 9:1 427ci with a good intercooler can run 10 psi, and maybe into 15psi, but of course it all has to work out between your compression, timing, boost, and fuel. I would tend to doubt that you could run a 427ci and 15psi with an a/a with only pump gas, that would be close to 1000 crank hp. I think that might be risky. I think that you can hit 700 crank hp to maybe low 800 crank hp (I'm not saying RWHP) on 93 pump but you have to be careful.

I was running 6 gallons of 112 and 1 gallon of 93 when I went out last time and went 144mph with 20psi. Keep in mind I am a stock cube 8:1 setup.

bifster

well race fuel is definately in the plans for the track dont get me wrong guys I dont plan on blowing this thing up cause of one stupid move. but I believe it should be a car at the same time so I want to be able to detune the engine a bit to handle the 94 and the street tires haha (drag radial) but i dont see the big problem with running higher compression when im gona tone it down on the street. what ever that may take even if im running 5 psi on the road it doesnt matter nobody around here willkeep up hahaha.

TINKRD

iTrader: (27)

Low compression = more boost/timing on pump gas before detonation
Higher compression = less boost/timing on pump gas before detonation

If you want to be able to run max safe boost on the streets w/ pump gas get lower compression. Then when you go to the track, turn the boost up and throw in some 104+ oct.

With my build (408ci/GT47-88), SCR is 8.5:1 and I plan on running 10lbs on 93oct for the streets and then 15+ at the track w/ 104+ oct.

Safest bet would be leaving the timing the same on pump vs race gas. Sure you’d be leaving power on the table, but it’d be the easiest safest for the avg guy who wants to be able to take it to the track w/ out having to switch tunes.

bifster

ok really when u factor in the numbers guys detonation is gona happen at the same point really... if you lower your compression ration it takes more boost to creat the same amount of cylinder pressure, as it would with a higher compression ratio and less boost. either way you do it the cylinder pressure on ignition or milliseconds before is what creats the atmosphere for detonation. I realise time after time boost will make more power but there is a difference between usable power and RACE power haha. race power would be the sudden spooling of the turbo and massive power gain as boost comes on where streetable or usable power is more linear and equal. no huge jump over the rpm rang normally within a few hundred HP instead of going from 200 hp low comprssiong to 900 hp low comprssion+boost. and really im looking for kindof the happy medium i guess. and was just wondering if anyone found a really good dual purpose compression ratio that gave them the flexability to have a well rounded Race/Street car

cablebandit

iTrader: (37)

yeah...9.0-9.5
after this weekend, ill do a couple of dyno scenarios and see where power is at 4.5...5.5...9.5 and 15 psi....open vs closed cutout. I cant use over about 700rw dynojet on the street unless i am rolling at highway speeds so thats why 700hp for the street is a good number for me to work with on my setup on the street

MIGHTYMOUSE

iTrader: (59)

im figuring 10:1 will only hold max of 700rw depending on cubic inches of course on 93 octane.

don't go hurting your motor doing this now..

Pro Stock John

iTrader: (34)

Sure 9:1 is a happy medium.

The next motor I do if it's for a race application will be between 9-10:1 since it would be pure race.

Websy21

iTrader: (34)

What about 8:1 with a 408 on 91 pump?