I have a nice 355 blower motor built that has right around 9:1 compression. I have a custom cammotion cam that's 223/232 and somewhere around .500 lift and a 114lsa. I also have an nx wet kit with all the extras and I've converted it to stand-alone with an inline 255lph pump, a 1 gal cell and a Weldon regulator.

I was thinking I should be able to tune it to make whatever power it can on pump gas on the blower and then bring on a 100-150 shot with 118 octane in the cell. I have a Mallory 685 box that can retard timing on juice and also on boost, so...???

Is this practical, or with the nitrous cause detonation despite the 118 enrichment fuel?

Also, I have been thinking about doing a meth injection kit. If I did this, I could probably run the 6.66/2.75" pulley set. However, would the meth interfere with nitrous in terms of difficulty of tuning? I ordered one of those PLX widebands yesterday and I think it's going to help quite a bit.

 

You may be marginal wrt having high enough octane to avoid detonation. Remember that when using the N2O the octane your motor will "see" will be proportional to the amounts of 93 and 118 octane. Probably in the range of 98 octane (assuming 20% the fuel is 118 and 80% 93). You definitely will need water injection (run 50/50 water/methanol) and it will not make it any harder to tune, though it will add another variable. The way to make the combo work will be to keep the boost in the 8-10psi range if you plan to use nitrous.

Rich

 

Rich, why would you want to keep the boost in the 8 to 10 range? Just curious. Thanks.

Ken R.

 

....to be conservative?????

Rich talked about avoiding detonation. 10psi and 150hp shot is a lot of cylinder pressure. Better listen to a guy that has 'been there done that'.


-Scott.

 

Thanks for the input guys. Rich, how did you have yours setup in terms of timing, boost, fuel and nitrous?

I have a 6" and 6.66" crank pulley and I think a 3.33 3.15 2.75 and one other blower pulley that's around 3". If I were trying to make 8-10psi on mildly worked heads, which pulleys should I try?

I have heard of guys who run 50/50 mix, but others run 80/20 and I haven't ever heard of anybody doing any kind of empirical research on the subject. Is there somebody who has done any controlled experimenting in this area?

I wonder if it would be smarter to use VPs nitrous fuel in the cell?

 

Mine is ~8:1 and I run 17-18psi with 100 octane unleaded. The nitrous is used at the track almost exclusively with C16 (116 octane). Timing is at 24 degrees maximum advance when under boost with very cold plugs. Pulleys are a matter of trial and error. As far as water:alcohol the best information I have is 2:1-1;1 water:alcohol. I run ~1:1 (50/50).

Rich

 

If you have a pump gas tuneup, what psi and jet size do you run on the meth? Have you ever tried to tune a small hit on pump gas, and is your nitrous enriched with the tank fuel?

From what I have read the meth should be around 100 psi for maximum dispersion. I'm probably going to order a meth kit. Did you pull fuel near WOT for the meth?

 

I'd like to hear how you have your system tuned. How was your car set up when it went the time in your sig?

 

It will run on 93 with no N2O. I never had the guts to try it with 93, boost AND nitrous. On the street, I use 100hp nitrous jets (it's a 2-nozzle setup) with the 100 octane. When used at the track (from which the car has been "retired") I used up to 250hp nitrous with the C16. With that setup I swapped in an old set of O2 sensors, though intermittent, occasional use of leaded fuel doesn't seem to degrade them.

I think you really need COLD plugs for boost plus significant amounts of N2O. I use an NGK with a "10" heat range. When I first went to these, I was concerned about fouling. But even with my unimpressive ignition system (Opti, MSD 6, MSD replacement coil) this has not been a problem. The top ring gap needs to be at the upper end of range. All IMHO. I am pretty conservative about motors.

Rich

 

nosfed, my previous setup with my sig time was on 6psi with nitrous jetting in the 40 to 50hp range. Keep in mind it's a dry kit also. I was running SVO 36 pounders with a racetronix 255 intank pump along with the holley inline booster pump. I tune myself, so my timing is pulled in my tune. I was running it around 28 to 29* on premium pump gas. Sounds high but never got any detonation. We can get away with a little more timing at this altitude I think also (5700ft). Ignition setup is a 6AL, hypertech coil, taylor 8mm's and AC plugs one heat range colder. Heads, cam, and headers along with that of course. I'm running 10psi on the new setup and will be upping the shot to 100 to 150, but pulled some more timing (now in the 24 to 26 range for now) and upped to 60# Semiens injectors. Also running the meth kit. I'm thinking it should run a mid 10 or maybe even lower assuming I have it tuned good and some good 60ft's.

Ken R.

 

Yes it will cause more difficulty. With boost, nitrous and methanol
the methanol wants to foul out my plugs so I have to run a hotter plug, cut back on the fuel jet and run less retard. With 104 unleaded in my gas tank, 116 in the fuel cell, 9.62:1CR, 14# boost, methanol on at 4.5# and a 100
shot I barely take out 3-4 degrees of timing. I still don't have the tune
completely figured out as I foul out a set of plugs every 4-5 passes. Alvin@PCMFORLESS did my chip re-programming.

Good luck.

Emil:93Z,383,Vortech,NOS,SNOW

 

If you run straight methanol, you are missing out on some of the benefit from WATER injection. The desired injection fluid is 1:1-2:1 water:methanol. I run ~1.5:1.

Rich

 

If there is any empirical evidence about an ideal mixing ratio, I'd love to see a laymans' explanation. I see that people have certain mixtures that they use, but I have yet to see anybody that has done any testing. It's easy enough to mix it 50:50 and I'm not trying to reinvent the wheel, but I am curious.

I bought one of the kits that uses the washer fluid reservoir but I'm not sure how to install a bulkhead fitting on that tank because I can't get my hand inside. Any suggestions?

How big a nozzle should I use for a mild 355 with a hot air S-trim and 12 or so psi on 91 octane? The place I bought this from told me a 600cc was needed, but the receipt says 300cc and the pump is 100-150psi (claimed).

I've pretty well decided to take the nitrous off the car. If I can't spray it on pump gas I don't see the point in having it. This car is a driver that will never run race fuel and I'm not interested in making passes at the track it can't do in everyday trim.

 

I'm running 8psi with a 150dry shot and a Snow meth kit on my 383. Using NGK's 2 heat ranges colder then stock with a non-projected tip gapped at .032. I run the meth kit with a 675ml jet at 150psi pump pressure and my Snow controller set to come on at 2psi and 100% at 15psi to cut back the meth/water a bit. Its also a 50/50 mix. This is all on 91 octane pump gas. Keep in mind that i'm at 5300ft elevation also, so think I can get away with a little less octane. I saw no detonation on the dyno while I was scanning and air temp was 90deg. Timing is set to 26deg also. Made 535rwhp/619rwtq uncorrected through a single 3" exhaust pipe going into my cat back. I need to free that up a bit but will also be running cut outs off the long tubes at the track so i'm sure the numbers will be higher then that. I'd like to go a few ranges colder on the plugs, but these are working for me fine at the moment.
As far as using the washer reservior, thats what i did for more capacity. You can install the fitting at the bottom of the tank fairly easy. I found it easiest to remove the plastic cover in front of the air dam under the tank and just remove the tank to install the fitting. I drilled the hole on the underside below the fill cap on the tank, then used a set of parts grabbers (like the ones you use to grab nuts and stuff you drop in hard to get places) and installed the fitting through the hole, then screwed on the nut on the outside and used Goop sealent on the threads and nut. You need the Goop that methanol won't eat away. No leaks at all and it's in there pretty snug.
I don't think you should bag your n20 kit. You should be able to get it to run without any issues. Even if you run a 50 to 75 shot, that will make a huge difference.

Ken R.

 

I agree about the value of a small nitrous shot. The amount of injection fluid is trial and error. Dynotesting is the easiest way, but it can be done at the track. Start small and keep adding injection fluid until it starts to run ragged and/or slown/make less hp. The original work on water injection was just that - straight water. It was found that ethanol could be added to keep the injection fluid from freezing but retain most of the benefits. But the basic idea was to use water for the reasons discussed in the gasoline faq: http://www.faqs.org/faqs/autos/gasol.../preamble.html (required reading).

"Some aviation SI engines still use boost fluids. The water-methanol mixtures
are used to provide increased power for short periods, up to 40% more - assuming adequate mechanical strength of the engine. The 40/60 or 45/55 water-methanol mixtures are used as boost fluids for aviation engines because water would freeze. Methanol is just "preburnt" methane, consequently it only has about half the energy content of gasoline, but it does have a higher heat of vaporisation, which has a significant cooling effect on the charge.

Water-methanol blends are more cost-effective than gasoline for combustion cooling. The high sensitivity of alcohol fuels has to be considered in the engine design and settings. Boost fluids are used because they are far more economical than using the fuel. When a supercharged engine has to be operated at high boost, the mixture has to be enriched to keep the engine operating without knock. The extra fuel cools the cylinder walls and the charge, thus delaying the onset of knock which would otherwise occur at the associated higher temperatures.

The overall effect of boost fluid injection is to permit a considerable increase in knock-free engine power for the same combustion chamber temperature. The power increase is obtained from the higher allowable boost. In practice, the fuel mixture is usually weakened when using boost fluid injection, and the ratio of the two fuel fluids is approximately 100 parts of avgas to 25 parts of boost fluid. With that ratio, the resulting performance corresponds to an effective uprating of the fuel of about 25%, irrespective of its original value. Trying to increase power boosting above 40% is difficult, as the engine can drown because of excessive liquid [110].

Note that for water injection to provide useful power gains, the engine management and fuel systems must be able to monitor the knock and adjust both stoichiometry and ignition to obtain significant benefits. Aviation engines are designed to accommodate water injection, most automobile engines are not. Returns on investment are usually harder to achieve on engines that do not normal extend their performance envelope into those regions. Water injection has been used by some engine manufacturers - usually as an expedient way to maintain acceptable power after regulatory emissions baggage was added to the engine, but usually the manufacturer quickly produces a modified engine that does not require water injection.

If you know someone who is an SAE member, get this paper: Water Addition to Gasoline - Effect on Combustion, Emissions, Performance, and Knock. J.A. Harrington. SAE Technical Paper 820314.

Good reading.

BTW: I don't measure too carefully, I end up around 1.0-1.0-1.5:1.0 water:methanol and it works about the same.

Rich