N2O vs turbo

[ebola]

I own a turboed vehicle with efi.Id like to convert it to fully mechancal ignited, carbed, with open flow, long cams and high compression ratio nitrous equiped drag race car.Its a turbo dodge daytona.Im trying to get any clue is it possible to reach at least the same hp/tq with N2O and any other fuel(race gas, alcohol, lpg) combined without forced induction(turbo or blower)??? Engine by nature is long stroke, cast crank, sohc, so its not designed for high revs.That means I can gain some improving good torque at rpm below 6500.Turbo does it perfectly, there are 400 hp designs with those 2.5 liter fourbangers, what I can only dreaming about, but...Id prefer to go N2O.I can afford strong internals, webber carbs(or four mikunis - last tough), pure methanol or race gas.I have a professional machine shop to support me, but...I doubt about design.And this delays things: what compression ratio to go for? Is dry sump any better for this application? Maybe I should try to get dohc head? If youd have any Ideas, Id appreciate it VERY MUCH!
Regards
Andrius

 

[Metalguy]

N2O can be great for drag engines-if the rules allow its use. It works even better w/methanol. Just keep things on the rich side!

 

[mpg9999]

A progresive controller is your friend.

Copied pasted from

http://www.sr20forum.com/showthread.php?t=59689

"...NX conservatively states that a typical stock 4 cylinder engine can handle a straight 75 shot with no problems. At 3000 rpms the torque added would be 75hp*5252rpm/3000rpm = 131.3 ft-lbs. So to be conservative we'll say your engine can handle making 230ft-lbs of torque without bending a rod. (Assuming you're hitting the nitrous while already accelerating the car). You want to set up you nitrous controller so you don't exceed this torque limit. At 6000rpms a 125 shot would add 125*5252/6000 = 109.4ft-lbs. You're way safe as long as you set the time on the controller to be hitting full nitrous by the time you're at 6000rpm. I use Desktop Dragstrip to help figure out time in each gear so I know how long to set the build time for. Its kind of a guessing game, but just work your way up and input your data as you go to match your real world runs as closely as possible. Anyhow, now that I have a reliable daily driver, I'm going to test my theory with a 150 shot next summer before I totally change my set up."

 

[ebola]

Thanks for info, but...what compression ratio is best for max shot? Cam? And methanol...concerning methanol is slow burning fuel, in correct ratio with N2O(oxydiser, fast burning characteristics) it might be good, but I found some info, that it doest work together...kind of too cool charge or other reasons...kind pump fuel is better with N2O?

 

[patdaly]

Ebola, I do not believe you will be able to reliably match Turbo'ed Hp with Nitrous on your combo. Nitrous ingested in serious quantities is hard on any engine, much less your combo. Shoot for as much Compression as you can get, I have no clue on Cams for your combo. I would look to Propane Injection, we have a very knowledgeable gentleman here, post a question regarding Nitrous use with Propane.
I do have to ask, why would you want to leave the precise control of EFI and a Turbo?

 

[ebola]

I am much more familiar to old engine managment systems.Carbs, mechanical injection, weights and vacuum advance ignitions are easy to tune for me, not as EPROM burnings and remaping modern ECU's. It is for younger generation...also I dont think it is nothing more to withdraw from an old systems...My way is to built in as much custom system and original, "my own" as its possible.
About turbo...I was thinking if Id like to boost it seriosly, over 2 bar, I need high oct fuel anyway.Without anticnock additives, high boost is impossible, with all possible high dollar hardware - IC's, ECU's,tuneble spark,Ill come to alcohol anyway.Now to use it with turbo and carb - nonsense.Blowing thru carb is complicated, draw thru system with alcohol to air ratio...also doesnt sound good, its so ritch...turbo would be under shower...Thats why I came to question - what about Nitrous? If Id built an engine with short bell carbs, long cam and 14:1 pistons? But again, people say - for high nitrous high compression is not good, kind of street compressions are better...Then methanol has no much advantage against gas.It looks like nitrous is either for big powerfull aftermarket block, blown monsters, or for stock street cars just to have some fun...Turbo is more powerfull for small engine isnt it?
Propane...I was thinking about it, but...if I use methanol, nitrous, and propane fuels...By the way - does propane comes to nozzle in liquid or gaseous consistence?

 

[Metalguy]

Again, for a drag engine N2O offers a lot. The engine sees it as "free" HP, since there's no extra exhaust back-pressure.

It works well with alcohol and even nitro. Your engine's HP is oxygen-limited-the more O you can get into the cylinders the more fuel you can burn efficiently. Some people even use it WITH a turbos.

BUT, follow Mpg9999's advice, and make sure you get someone with a lot of N2O experience to help you.

 

[patprimmer]

You can use methanol as the basic fuel, but if youenrich with alky to compensate for the nitrous shot, you run the risk of cooling the intake charge so much, it doesn't evaporate properly, then it doesn't burn properly.

Both alky and nitrous have high latent heat of vapourisation values, but petrol has relativly low latent heat. Cold charge is good to a point, but you can go to far.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Metalguy]

Have to disagree, Pat. Nitro runs MUCH richer than straight methanol, but under load it burns just fine, with little evaporation beforehand. It doesn't idle well at all, but as soon as there's a load on the engine, it ignites even with a tiny .015" plug gap. I suspect the poor idling is caused more by the tiny gaps than from lack of evap.

 

[patprimmer]

I am talking nitrous oxide, not nitro methane.

Nitro methane is a whole new subject with a whole new set of problems.

It does not burn when liquid. The vapours burn in the presence of liquid, and evaporate more liquid etc etc. I expect that is one reason it burns so slow.

The slow burning is the reason nitro motors don't like to rev real hard.

The wet mixture is very hard to ignite, and that is why nitro motors need special extremely high power magnetos.

They use twin spark and twin maggys for two reasons.
1) To help overcome missfires at lower speeds.
2) To propogate two flame fronts and increase flame spread and burn speed during launch.

Once well under way, the heat generated and the relatively low octane of nitro gets it into detonation, where it self ignites and often blows the tips off the plugs well before the end of the run. You normally need to shut down the fuel supply to shut them off at the end of a run.

Regards
pat

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Metalguy]

Pat,
The orig. question involved N2O, and I got nitro involved because it's sucessful use both with and w/o N2O should refute some other replies here.

I wasn't aware that nitro motors didn't like to rev. I've seen a BBC turn over 9,000 RPM with a 60% load of it.

Standard low-current/low energy mags. with their characteristic slow voltage-rise time will easily ignite a 60% nitro/meth. mix in a 2,000+ HP BBC, even with a tiny .015" plug gap. High power mags. are "extra" insurance when a win means $$$$$$$.

Dick Landy used to run two spark plugs/mags. on a gas motor. *I*tried that on a 1 1/2HP Clinton lawn-mower engine I had way back around 1956, when I was 15. Had my BIL machine a new head for it. At that age, I wasn't aware that the single mag. wouldn't fire BOTH plugs--but I learned from it.

Finally, nitro motors don't use plugs with "tips". The center electrode is WAY recessed, and the side one is really from the side-it comes in thru the threaded area.