Lean Tune ups

General Nitrous Discussion

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John_Heard
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Lean Tune ups

#1 Post by John_Heard » Tue May 17, 2005 8:47 am

I read some posts a while back, maybe over a year ago from Patrick Budd (Procar) where he was discussing a technique he called lean tune or something like that. Basically the idea was to start lean and with a lot of timing out, then slowly add timing and fuel putting heat into the cylinder till you find the the sweet spot. According to Patrick some of the other NSCA guys (Musi??) showed him how to do this.

What do you guys think about this technique? I can see how pulling timing out will cool the cylinder down a lot. Do you see an advantage in doing it this way? Have you heard of doing it this way before?

John

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#2 Post by amature » Tue May 17, 2005 11:57 am

My motor prefers fuel and timing. I've tried quite a few different combinations and it always comes back to it likes to be a little fat with timing rather than lean and less timing.
- Greg

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tuning

#3 Post by Ron Clark » Tue May 17, 2005 4:00 pm

this technique basically allows you to learn what your combustion chamber/nitrous load/rpm limits are...thats the key...each COMBIINATION WORKS DIFFERENT.....you do not need any more fuel for nitrous than a normal engine, providing you can burn it effectively without "spikes"..its those anomolys that kill you..you need to find out where the chamber wants to fire for best results..even small changes in quench can mean disaster if you change combo and leave tune the same..years ago musi and i discussed what he was doing in some dyno testing..he had big compression and was down to +2 degrees total timing at speed..most folks would laugh at that, but he was making 2000+ hp

anyone that tells you you need this much timing, and loads of fuel isnt tuning you, just giving you a hopeful start..all nitrous tuning must be done by the end user..those who learn the medium will dominate..if i flow a system for you, i can give you a really good start, but i cant tell you exactly where timing should be for you engine and rpm..you must do your own testing to determine that

i really like the idea of the "lean tune"..been spouting the basic technique for years... 8)

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#4 Post by amature » Wed May 18, 2005 12:43 pm

Out of curiousity, how does it allow you to " learn what your combustion chamber/nitrous load/rpm limits are"?

I've always started with an approximate tune, tested, logged, then went a bit richer. If the results weren't better, I went a bit leaner. Then do the same thing with different timing. I've never felt the need to start out lean with little timing and go up from there. I've found my engine's happy spots without going to the "limit" or extreme. For me, if it makes less power going leaner than my last setting (with various timing changes), why would I go even leaner yet?

What is the benefit from lean tuning versus what I do?

Also, what do you mean you don't need any more fuel for nitrous than a normal engine? Are you talking overall AFR of the combo? My engine likes to run hot and rich N/A (mid 12:1). On nitrous it likes to be low 12:1 - high 11:1. At least that is what the time slips show. Though as for fuel consumption, high 10s to mid 11s isn't much of a jump in most peoples minds.

I have a question on timing. I've played with it quite a bit but have some basic concept questions. When the RPMs go up, there is less time the A/F mixture has to do a complete burn, therefore, it would make sense to advance the timing as the RPMs increase. Is this the case? I know many people who take timing out as gears shift up due to the load, but what about with adjustable timing now days, would it be best to find a nice upward overall curve? That is, though there is a drop when there is a shift, there is still an upward curve as the RPMs increase. What about when nitrous is introduced? It cuts the burn time down by nature. Therefore you don't need nearly as much timing. But doesn't it still hold true that as the RPMs increase, there is less time to burn, therefore a timing bump makes sense. Start throwing in a progressive controller in the mix and it all gets complicated!

So much to learn... I need to get my car back together so I can start testing and learning again. :)
- Greg

ron

tuning

#5 Post by ron » Wed May 18, 2005 5:56 pm

your going at it correctly..its all about testing..as for timing, most engines respond to less timing as rpm increases..there are several reasons for this..like the cylinder pressure is down due to less fill, and residual chamber heat..does nitrous increase the "burn speed" of gasoline?..

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#6 Post by Racer704 » Thu May 19, 2005 6:30 am

As Ron stated it really depends on your application, I know alot of Pro-Mods add timing back to there engines at a certain RPM and thats how they started to get the big MPH in the 1/4. But like all tunning it should be done for your car not what your buddy did to his and in small steps to see what changes have taken place.
Johnny B.

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#7 Post by Bobalos » Thu May 19, 2005 9:01 am

if your running on the jug, one of the reasons why adding timing on the big end works so well is that the bottle pressure starts to drop down a bit, making it fatter. adding a bit of timing back in helps to burn that where its helpfull (not in the pipes).

Bob

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#8 Post by amature » Thu May 19, 2005 11:30 am

Thanks for the good info. I didn't even think about how much A/F mixture gets ingested at higher RPMs. Starting to make sense now.

As far as burn speed with nitrous, yes, the rate of burn does increase as the nitrous is added.

I'll have to start playing a little more with my digital 7.
- Greg

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the "tune"

#9 Post by Ron Clark » Thu May 19, 2005 11:34 am

fun fun fun..barbs telling secrets..which is good..his system will really help with conventional problems such as pressure drop..with a variable orifice noid you can compensate for pressure drop by opening the valve farther...and then turn the fuel up or down as you see fit...the true beauty of the "tunable " system isnt in its max power, but in it's ability to stay efficient...

timing will change with every rpm and load... 8)

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#10 Post by Bobalos » Thu May 19, 2005 11:36 am

I thought briefly about adding more timing in with my ignition as it goes down the track, but I dont think that @ my level & with what I am doing (just playing around really) that it matters. if I need a bit more HP, I will just pill it up (or stop eating double whopers, LOL). It would be an interesting study though.

On another note, I yanked the plugs out of the car last night & they all look GREAT. I am VERY happy with how it ran the last time out. I need to cut them appart & see if I cant get my digital junk to take a good picture of them.

Bob

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