Nitrous question

[TURBOZ]

I have a speed pro computer on my turbo motor. Since i have control of air/fuel I will be running a dry system. What kind of air/fuel ration do most of you look for? How much timing does one typically take out with a 50 shot? What are your intake temp while on the juice?

Thanks

 

[bobc455]

Well take this for whatever it's worth.

I have an NA motor with nitrous & a Speedpro. On the dyno without nitrous, I found that my best A/F ratio was 12.2:1.

I assumed this would be the same with nitrous. However the motor is now out of the car awaiting all new pistons, I'll let you figure out why

Actually there are a few other possibilities for my problems.

1) When I gapped the plugs, I used regular old pliers- this made little marks in the electrode that may have turned into a hotspot causing preignition.
2) I run 36 degrees timing, about 2 more than most people with my combo (most people run 34). I only retarded 4 degrees on a 150HP shot, and I should have retarded 6. Add that to the 2 degrees extra advance that I run, and my total timing was 4 degrees too far advanced.
3) I didn't use any race fuel, pump gas only (although I'm told this shouldn't be a problem since my compression is only 9.6).

From now on, I'll be running 28 degrees timing, a target A/F of 11:1, and probably some race fuel (at least at first) when I'm gonna hit the button. I'm also told that the Autolites are the best plug for the juice, so I'll be switching to those with a 0.027" gap (gapped with a proper tool).

I don't track my intake temperature, so I couldn't tell you that.

More info that what you asked for, but maybe you'll pick up on something

-Bob Cunningham
bobc@gnttype.org

 

[TurboTR]

Good gosh yes, race fuel only please After my plug gaps closed up with 18 psi boost on 99 oct "race" unleaded with the S1/GN1's engine I swore off trying to save a buck on fuel and have not had a fuel related problem like that since, thankfully. Other than a slight pain in the wallet.

I watched a guy pull a plug out of a stock 240sx Fri night with totally missing ground electrode 75 shot with pump gas. Probably too lean IMO. Silly Zex setup. Plug porcelain looked very white to me too, meaning it's way too hot a plug to begin with.

The rule of thumb for retard is 2 deg/50 hp, but I'd say don't be shy about removing say 3 deg/50 hp if it feels better. The juice will more than make up for the 1 deg of extra retard I plan to get the cyl pressure gear on it asap and see if the rule of thumb is really enough for mine with the juice on.

FWIW I ran a target of 11.4:1 with juice on. Thankfully it gave good results, but will probably go even richer next time, like 11.0:1 range as long as it doesn't make it misfire. I want to know that the hot oxidant has plenty of hydrocarbons to bind with instead of metal ;-) C16 fuel only. Plus, NGK -7 or -8 heat range plugs start to look "right" in it for wot duty and don't cause much compromise on the street IME.

Anyone else remember dropping hot steel wool into a test tube of ~ pure oxygen in science class in grade school? Whoosh! ;-)

TurboTR

 

[Schlodes]

Deja vu!!

Originally posted by TurboTR

I watched a guy pull a plug out of a stock 240sx Fri night with totally missing ground electrode 75 shot with pump gas. Probably too lean IMO. Silly Zex setup. Plug porcelain looked very white to me too, meaning it's way too hot a plug to begin with.
TurboTR

Wow.. I've got a better one! I installed a Zex Kit on my buddies 2001 Honda Civic. Started out with the 50 HP jets, 94 octane pump gas.. Car loved it, and ran great.. was zippy for what it was.. Left the timing stock.. I told him that at the track with some 100 octane no lead, he could probably sqeak by with using the 75 HP jets minus a few degrees of timing.

I see him up town at a stop light one day, and he starts grinning real wide. I says "you didn't.....". He says "Dude.. I put the 75 jets in dude..". I said: "did you take out 2-3* timing??? Ultra 94 I hope??". He did.. and yes to 94..... and asked me to hop in and go for a spin. So we pulled over and I did. He took me out for a 'spraying' and it felt real good.. I was suprised that a bone stock fuel system on 94 octane gas was handling this. But it seemed to be OK as I couldn't hear any audible knock. Later that night, he raced a Dakota RT with K&N and Flowmaster exhaust and his Civic SLAUGHTERED the RT badly.. Then raced a 90 LX 5.0, 5 speed with the same mods as the RT.. K&N and Flowmasters.. and the Civic had him until about 95 MPH then the Mustang creeped by slowly...

Then after that night... I bumped into him a few days later and he told me that he was too lazy to drive to the Sunoco station (no Sunoco in town where we live - bout a 15 minute drive to get the Ultra 94 which I swear by as far as pump gas) So he used Shell 91 instead.. and that "fuel octane doesn't matter" because he sprayed the 75 HP shot a few times around town so far and it still runs great.. I said that he was stupid for even trying that, and NOT to ask me for any more help or advice because he won't listen anyways.

At this point stopped talking with him as far as what he should do to his car.

About 3 weeks after all this, I am at the track.. He shows up with his car and some ricer friends. Made one pass in the 15s that day. Rest were all 17.90s..[slower than a stock civic] Come to find out the LOSER put in the 100 jets b/c he was mad that the car was going so slow, and melted [more like finished off what was already damaged] some valves... there was a hole on a few, and I guess one valve broke apart.. Not sure.. I dont talk to him much now. Someone told me he went to check his plugs... and it was the same as the 240 SX guy... They did a compression check at the track and one cyl had ZERO..I was told.

STUPID. Car would have been a 14 second car at one point before he ruined it.