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Old 20th June 2005, 23:06   #1
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Lightbulb Compression Ratio and NOS

Hey Guys,
Need some info regarding Nos to be used in two similar engine with same CC but different C.R
eg

if we use a 50 shot Nos in a Honda 1.5 L with stock c.R and another Honda 1.5 L whose C.r has been raised to 11.0
will power produced will be same or different ? assuming both engine has undergone similar modification , will any timing retard be required for higher C.R engines or any additives apart from higher octane fuels ?
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Old 21st June 2005, 11:22   #2
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well, i think, that a higher compression ratio city will actually produce more power, lower down the rev-band; but you are running the risk of detonation at higher revs- whereas the lower compression city will be a more safer bet. but if you have water injectors embedded in the head, then the cylinder could be safer, and the risk of detonation could be less.

but, for a 50-shot nitrous, increasing the compression ratio might not be that good an idea. for a 35 shot, maybe.....;not 50 shot; unless you have reinforced the block, alloyed the bores, and have forged pistons, conrods, et.al....

so, porting and polishing the 1.5 head, improved breathing, retaining the same compression ratio and running 50-shot nitrous and water injection will give you more reliable, and better results than running an increased compression ratio head with the same mods.

lower c.r's are required to prevent detonation. testimony to that fact is that dragsters and funny cars, both producing around 4000-6000 bhp+ with methanol as the fuel, run on 6.9:1-7.5:1 compression ratios.

but, if you wanna go in for 50 shot of nos and 11.0:1 C.r, then the fuel will have to be 97 octane, at least- otherwise, you are running a risk of blowing a hole through the pistons....

Last edited by veyron1 : 21st June 2005 at 11:26.
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Old 21st June 2005, 11:40   #3
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If you are upping the CR, you would need to retard the ignition or/and find some really good fuel to cope with that. By running an increased CR AND NOS, you are efffectively raising your CR even more.

In our conditions - read lousy fuel - I see that more as a disadvantage, as you will just end up with an engine that detonates rather than any meaningful increase in power.
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Old 21st June 2005, 12:13   #4
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I guess Veryon and Rtech have already mentioned the facts however please realise higher the comp the stronger the bottom end required and higher the octane of fuel hence you would tend to run a smaller shot of NOS right in the power band where you need it.

You have to retard the engine based on the NOS shot you will run.
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Old 21st June 2005, 12:27   #5
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pardon my ignorance...but what are water injectors?
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Old 21st June 2005, 17:54   #6
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Quote:
Originally posted by v1p3r
pardon my ignorance...but what are water injectors?
water injectors are pumps with nozzles that inject water into the cylinder in the form of a spray, so that detonation, knocking, and overheating inside the bores (the engine itself) can be controlled. by installing water injectors, you can reduce the risk of detonation...and also, you actually increase the power output, as the engine runs cooler (the mechanism itself doesn't deal with the engine's thermal efficiency or heat transfer characteristics- the device only helps in maintaining controlled combustion, thus helping in avoiding detonation), and keeping the cylinder in optimum operating efficiency.

this mechanism/ device (water injectors) are used in high- performance cars, that also have to cope up with high pressures, like NOS induction. i've seen some skylines and supras, (on the net, of course) that run these systems, alongwith CRYo2 system; also seen some citys and lancers that run with these...
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Old 21st June 2005, 18:06   #7
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water injectors would not really be needed on our engines. NOS itself has a cooling effect if you will, as the nitrogen lowers the temperature inside the cylinder.
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Old 21st June 2005, 18:19   #8
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Quote:
water injectors would not really be needed on our engines. NOS itself has a cooling effect if you will, as the nitrogen lowers the temperature inside the cylinder.
but, IMHO, when you release N2O into the combustion chamber, the combustion that already takes place from the gasoline is accelerated, therefore increasing the temperature inside the cylinder- which is why, the water injection mechanism should be fitted onto any engine that's running more than 50 shot of nitrous and has a turbo running a boost of more than 7-9 psi. the temperature inside the bores, without NOS, or any other mods, runs between 800-1200 degrees at the igition point; add nos, and youre looking at a good 1400 degrees... which is why, water injection should be added considering the bore size and the amount of mods you're subjecting it to, and not just cubic capacity- a maruti 800, having a 798 cc engine, with a 35 shot nitrous and a turbo running 5 psi boost would certainly require water injection- whereas, an accord running the same boost and nitrous configurations wouldn't(35 shot, and 5 psi).
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Old 22nd June 2005, 23:00   #9
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Thanks for the info guys, i had doubt the stock internals would take so much pressure, I agree with Rtech Water injections are more useful for turbo,s , cause when nos is activated due to its properties the temprature in combustion chamber drops significantly
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Old 28th June 2005, 03:13   #10
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actually you would not need a water injector jus increase the length of the cooling pipes and put more coolent it will be fine but if u put a water injector the performance will be decreased
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