First off I have never owned a boosted car, this is just my opinion on the matter, I have seen more and more people talking about higher compression on boosted motors. I do not claim to be an expert so again THIS IS ONLY MY OPINION


Pump gas on 10.5 or 9:1 could both benefit from Meth injection. This allows you to compress the air more before it ignites or detonates. Higher compression on a boosted build IMO seems like a passing fad. Yes you can make great power with less boost. But to me if your building a boosted motor go ahead and lower the compression.

With a higher compression ratio your going to have more cylinder pressure all around. In and out of boost. This is can be great for you out of boost, but this causes heat and also makes pushing water more likely (more likely than it already is with a turbo forcing air into the combustion chamber) when under boost.

People will say stuff like it makes the motor not as much of a dog out of boost.

This is something that I think it overplayed because:

1- a properly sized turbo will spool very well giving you a better torque unmatched by anything other than a large nitrous shot down low.

2- I just plainly don't think it is worth it. Your tune has to be very good and you have to use higher octane gas to raise the flash point of the fuel to a safe level or a lot more methanol to get the air temperatures down to an acceptable level to prevent detonation.

Yes, I know high octane and meth are both used to combat that very issue. It just doesn't make sense to me.

Sure slapping a procharger or turbo on a stock bottom end that's at 10:1 running low boost... go for it. When it lets go forge it with lower compression pistons and crank the boost up. If your building the motor to swap it in, why not just build it around 9/9.5:1.

 

Huh......If I can do 18-20psi with 93 pump gas and not detonate I'll just do that. Then I can get gas anywhere, anytime.

I have no problem doing 9:1 cr with a 408ci.......because I'll make sure the turbo is matched perfectly and will spool fast.

I'd rather not use race gas.......I just thought it was safer. I like the idea of not having such high pressure all the time and higher heat all the time.

.

 

Well you have to understand that race gas and spraying meth do the same thing they just go about it in different ways.

The problem is when you compress the air it heats up.

Race gas has a higher octane. Most people thing this means the gas like burns more or something, but actually it means it has a higher flash point. Meaning it takes more for it to ignite. Same principle is applied to why sports cars are only supposed to run premium gas from the factory. Run crap-o 87 and you might feel a little drop in performance because of pre-ignition.

Meth cools the intake charge, while condensing the air in the intake tract. This allows for greater expansion in the camber as well as allowing more boost to be ran.


I would set a power or ET based goal versus a goal based off of boost pressure. But just fwiw check out this post.

https://ls1tech.com/forums/16414508-post13.html

 

Interesting....17psi and 1,000+ RWHP on a 408ci.

So you would use Meth no matter what.....9:1 cr on 93 octane? Cooler the charge the better no matter what......

Fine with me, I'm not opposed to useing it. My fab guy who built his own turbo kit wants me to use an A2W IC too.......

.

 

Yep, set to a boost referenced pump. I thought air to water was only good for like once pass down the track before you had to fill it with ice again? I'm only familiar with A2A being used for street set-up's.

 

You can run normal temp tap water in the A2W and it will keep the IAT's cooler than an A2A especially on a hot day like this. Locate the water tank in side the cabin of the car like Mighty Mouse did and it stays the temp of the cabin. Then at the strip add ice and a little bit of water and make a pass.

I woud shoot for 9.5:1 just because it's a street car. Mighty Mouse also ran straight M1 methanol along with his A2W to get as much octane as possible from the cheaper methanol and more IAT reduction from the A2W.

I wouldn't use anything smaller than a T6 GT91 1.23 AR 98mm turbine turbo on a 408. I would personally use a S500SX88 with the 111mm turbine and a 1.0 AR housing. I prefer a larger turbine wheel and tighter AR housing as the turbine wheel is always the choke point on a turbo. The AR can change the characteristics of when that spool happens but can't relieve the amount of backpressure created. It can manipulate when the highest amount of BP is created but not the total amount if that makes sense.

And I will gladly take you up on your offer!

 

I'm curious as to why you think a nitrous car and a turbo car (both making 800Rwhp, all else equal given the setups) the turbo car would be faster from a roll...? I understand that lag can nearly be eliminated but it will still have a small amount, none with nitrous.. Nitrous makes more power under the curve, and the same torque... All instant.

 

A lot depends on the turbo as well. The a/r housing being used will determine a lot. I think the race between the n20 car and the turbo car will be very interesting. It will be easier for the turbo car to up the power if need be however if a eboost controller is being used rather than swapping jets.

 

Pressure drop would be my guess.

 

Nothing a properly heated bottle or Nano system can't take care of.

 

Nano yes, properly heated.... ehh.... I still think after a few highway runs on a 300 shot pressure would become an issue with out nitrogen assistance.

I'm not tipping my hat saying the turbo car would run harder. There are plenty of nitrous cars that run really hard and were build for highway pulls.

I was just saying nitrous vs turbo, if were are pointing out the weak links in either set-up on a nitrous set-up it will always be a pressure issue.

 

I can agree with you there.

 

I have seen two cars one turbo one nitrous that both make the same amount of rwhp on the same dyno run each other on the highway and the turbo car wins.

Not only would the pressure drop from the 300 shot be a hinderance, but the nitrous car unless it is a solid roller, or a high rpm(7000rpm+) big cubic inch motor that can really breathe up top in this instance racing the turbo car with the same amount of power would be the only way it would win or be even.

Yes the nitrous car makes more torque, but if you've ever seen a dyno graph of a nitrous car unless it's again an extremely high rpm motor that instant torque falls off a good bit and then you have to shift.

The turbo car makes TONS of mid range torque also and will continue to pull just as hard if not harder up to the end of the race.

Ever wondered why a nitrous car with the same amount of rwhp as a turbo car might e.t. better but not mph as fast as the turbo car that didn't e.t as well?

It's all about how the power is used and how the power curve is utilized.

Most big cubic inch or even moderately sized nitrous street cars just don't make power past 6700-6800rpm where as a turbo car due to it being a turbo and the way they ingest air and fuel are able to carry the power later in the curve than the nitrous car before they fall off. Again unless it's some crazy hydraulic roller motor or a serious race motor or insanely light car the high end power just isn't the same nitrous vs. turbo.

That's another reason why similarly powered and weight nitrous car can 60', 330' and hit the 660' e.t. wise quicker than a turbo car, but not run the same out the back to the 1/4 and mph traps as a turbo car can.

If you could own a turbo car that trapped 112-113 in the 1/8th and then own a nitrous car that trapped 112-113 in the 1/8th you would really understand what I am talking about and that isn't a dig or put-down please don't take it that way I'm just speaking from experience.

Another good example is a street bike. Whenever I would race them in my turbo car from 20-80 they always got the jump on me(light weight and amazing rpm acceleration in the lower gears). From 80-100 that gap would close and I would start to gain on them(gearing and power band also vehicle weight hurt me on the bottom end)then past 100 I would begin to walk on them and after 120 it was the other way around from the beginning of the race and at 150-160 they'd be pretty far back.

In a race the most average HORSEPOWER wins, not torque. I know hp is a mathematical formulation based off torque but once again unless you can carry all that torque past 6500rpm you won't pull the same as a turbo car.

Ever heard that turbo cars can take the same motor that was once n/a and extend that powerband 400-500rpm on top of that? It's very true. They continue to pull as the air is forced into them at a much higher pressure than the nitrous is ingested. Even though nitrous is pressurized it's still at atmospheric pressure where as a turbo isn't. It's well above that.

The most average HP wins a race and it's really just as simple as that.

 

With a correct setup, pressure drop should be about as big of a deal as lag would be in the turbo car.

I have been around enough nitrous and turbo cars that run quicker/faster than 115mph to understand (several close friends that run right around those times and much quicker).. I kind of took for granted that the nitrous setup at the levels we are discussing would be a larger CI motor that can breath 6700+.... Correct setups, same goes for the turbo.

Bike isn't a fair comparison as the aerodynamics are a joke... It has nothing to do with a turbo car racing it, a nitrousblower car would have the same results 120+.

I don't see a turbo car putting a hurting on a nitrous car (all else equal) in a 30-140 race... The nitrous car is going to jump out on it and the turbo car will have to play catch up. Will it? Possibly/probably, but momentum is very hard to over come. I would rather get the jump then have to chase.. We will take for granted that there in no lag the turbo car has to deal with, for its sake.

To be fair... If we want to talk about pressure issues, we might as well talk about lag issues.. Or boost leak... Or whatever else. In correctly set up combinations though neither should be an issue in a race as such.

 

Also if the bike is no comparison because of aero why the hell did it fall off after 80mph?

Power to weight only works so well for so long before raw hp overcomes it.

Just like getting the initial surge of torque from a nitrous car.

This is why nitrous cars in heads up racing are allowed to weigh less than turbo cars and thus the only way to make it equal.

Ever seen a nitrous car in heads up racing get the jump on a turbo car and both of them have very respectable 1/8 mile times only for the turbo car to overtake it and out mph it in the 1/4?

Tell me how that won't happen on the street.

When you figure out why it won't happen I'd love to listen to your theory.

I have raced PLENTY of nitrous guys with my old turbo car that thought the same way you did when they asked how much power your car make? Then asked how much does it weigh? Then when both are found to be nearly equal if not identical they want to race.

Then when I ended up walking on them and beating them by a car or two after they pulled an initial half a car they always wonder why it happens and I have to explain this same thing I am explaining to you right now.

 

Lemons, sorry I posted what I did in my first response.

I was upset as I felt like you weren't listening to the good examples I had given.

You seem like a sharp guy and you do know a lot about LS cars.

I apologize for my rudeness. I can swallow my pride when I feel like I am wrong or I was out of line.

No hard feelings? I hope you accept my public apology after your PM.

Thanks,
Martin

 

All good my man, its the interwebz, egos get inflated sometimes.. If we weren't right all the time.... Where would be?

However...... I was listening, I just had better examples!

Same goes to you man, you have some of the best explanations as to WHY people should choose "XXX" over "XXX". I hate taking someones word on something with absolutely no evidence as to why.. And if someone doesn't know why I should go with "XXX" part, they shouldn't be recommending it in the first place.

No grudges held here!

Agreed to disagree.. Hell, I'm probably wrong anyway... But I gave it a hell of a run! LOL

 

Damn intrawebz always getting me riled up for no reason.

I say we let the OP and his buddy find out for us once and for all!

Thanks for the kind words also. I try to explain as much as I can. I get some haters from time to time that tell me I talk to much which I admit I do all the time lol. I guess I try too hard sometimes, human nature I guess.

Cool deal, don't forget to take me up on my offer if you ever need help on your 370 nitrous deal.

 

HA... There was a reason all my friends begged me to get the FAST "Big Mouth" TB when it came out!

 

One thing to consider when talking highway vs 1/8 mile on a nitrous car vs a turbo car. Is that nitrous is injected at a constant rate.

We all know that nitrous has more oxygen than air. This is what make the power right? Nitrous is a chemical oxidizer.

When it is injected as soon as you go WOT of a switch set at say 3000 rpm at that moment the engine is seeing more nitrous vs the amount of air being pumped into the engine as the RPM's go up. This is where the drop off comes from. As the engine speed increases the mixture of air vs nitrous is more equal than when the engine is at lower speeds. So the max power output is going to lower than the amount of torque available right off the hit. This issue is independent of any pressure issues and is just a function of how the engine works.

There is only so much air and fuel an engine can use at any given RPM. This can even been seen when looking at how engines make their power naturally aspirated. A big cam motor has to spin higher in order to pump enough air to make the power the cam specs are sized around.



Taking a peek at this dyno graph shows us how there is more oxygen from the nitrous present at the lower RPM's and as the RPM's increase the higher oxygen content of the nitrous gets limited because not as much nitrous is making it into the combustion chamber as the valve events are happening much quicker.