NOS with exclusively methanol on a HC engine

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DaviesDJ
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NOS with exclusively methanol on a HC engine

Post by DaviesDJ »

I realise this is a bit left field from my most recent postings - but thinking about my latest build and CR etc - and I am a fan of high CR NA engines - my current rover is over 10:1 and the chevy I am building 383 with flat tops - is heading for about 11-11.2:1 CR - good to maintain. Pressures on a big overlap - but not so good for detonation on NOS

I run NOS currently and intend to always do so- and was thinking that in reality I may be limited to by NOS addition on high CR. But then I though - what if I had a separate methanol tank to be wet injected with NOS (no petrol) when the nos is activated ???? Would this allow me to use much more gas?? Thinking obviously a richer mixture will be required ???? Or not??? As detonation will be reduced. Chemically obviously ,ethanol wants far less air - but with NOS??
What sort of AFR?? Especially as petrol is being used but the NA engine and methanol and NOS is injected at boost? Has this been done before??

Interested in hearing what you think

Cheers

Dave


Spent so much on trial and error!

DaviesDJ
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Post by DaviesDJ »

Another option perhaps could be an ultra high octane race fuel - only small amounts would be needed - so 100 pound drum of 120 octane VP would probably last quite a while - and allow pump gas to be used normally. Methanol is cheaper though, it's the mixture and practicality that I am thinking of.
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crayefish
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Post by crayefish »

Why not just go for nitromethane? :)
Zander

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Post by mgbv8 »

I'm no chemist Dave!
But I think you are over thinking the issue ?

If you decide to run a separate fuel supply for the nitrous then use normal pump gas and add Power Pour for det supression.

Nitro isnt a simple additive to use with nos and get the settings right as it tends to make afr quite rich. Much more than petrol i think. ?

On a small engine like the ones we use you need to off set peak cylinder pressures to protect delicate parts. So if you want more power you keep retarding the ign timing and adding more fuel or fuel with a det supressor additive. A mate of mine with his 9 litre drag car found his sweet spot at 22 degree's after top dead centre on nitrous. He was running around a 750 shot back then i think?

Det supression is important due to the damage it can cause. But whats the point of supressing Det if the peak cylinder pressures just blow the head gaskets out ?

As far as I know you would need to use a shed load more meth or nitro than normal petrol with nos to get the same result. So from my point of view thats a lot more stuff to squeeze into the chambers to make power ?

All you need to do is make more use of what you have. Whats the difference between say 15 degree's BTDC and 15 degree's ATDC with regard to piston height in the chamber ??

I'm thinking not a lot ?

So if you ignite a big fat charge with a fast flame front at the above ign settings which one would give you the best power ???

Perry Stephenson

MGB GT + Rover V8

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Now looking for 8 seconds with a SBC engine

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stevieturbo
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Post by stevieturbo »

Basically sounds like a fairly normal water/methanol injection setup ?

More common on boosted engines, but can be used on any.


Methanol offers great knock resistance and cooling.

Water offers infinite knock resistance, but obviously doesnt burn

So you could use either, or a mixture. You wouldnt need huge amounts, so just tune to normal AFR's and you'll be fine.
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DaviesDJ
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Post by DaviesDJ »

Pel, you are spot on!!

I am over thinking the issue. I already add toluene to pump gas to avoid detonation, and I think I should just carry on with what I am doing with both rover and chevy setups

Think I will play by ear - as you say - just gently work my way up - have thought about methanol/water injection - and could always turn to this - cheers Steve.

I think that when I start pondering about these things I should just be ignored!!;-)

Am just at the point of setting out CR etc on my new engine hence this issue creeped into my head.

Thanks again guys!!

Dave
Spent so much on trial and error!

kiwicar
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Post by kiwicar »

Hi
Methanol is meant to be very difficult to get to work with NOs, Methanol has a relatively high disassociation energy and a high latent heat of evaporation, you are then going to chuck in nos at -150 odd degrees C guess what, you can extinguish the ignition in the cylinder and the charge basically passes straight through. On methanol pro mod cars that use NOs as the power adder they use race gas injected with the NOs and progressively shut off most of the methanol as more stages come in. I'll take my methanol tuning book along to the pod so you can have a read of the relevant bit.
best regards
Mike
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kiwicar
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Post by kiwicar »

Hi Dave
another thing to consider is that with the basic spec you seem to be aiming at with this engine, heads, cam spec and CR and with the inlet manifold you were looking at with EFI and mapped ignition you will be looking at 480 to 500 bhp, with out anything else, that cast crank, even with a shot peaning and a cryo treatment if you stick much more than a 75 or hundred shot at it your crank will snap. A 75 to 100 shot into a set of big port chevy heads on a chevy of this capacity will give enough detonation suppression just as a function of cooling the charge to not worry you, maybe retard the ignition a bit around peak torque on a second ignition map but I wouldn't bother with anything else.
See you in the morning ?
best regards
Mike
poppet valves rule!

DaviesDJ
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Post by DaviesDJ »

Mike - the plot has thickened! Have sent back the cast crank due to all this musing! And for an extra 300 quid I have/am upgrading to a fully forged scat crank and rods!! So going for the future proof- bullet proof setup;-)

So perhaps not quite as basic as before:-)

Will chat tomorrow - but think I will stick with high octane petrol for the moment!

Cheers mate

Dave
Spent so much on trial and error!

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