How fat is to fat

General Nitrous Discussion

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Re: How fat is to fat

#16 Post by John_Heard » Fri Jun 26, 2009 6:21 am

Deborah - when you've seen pistons fail like that (ring land), do you typically see detonation evidence on the bearings also?

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Re: How fat is to fat

#17 Post by 71Hellride » Sun Jun 28, 2009 10:16 pm

The theory I’ve heard is that extra fuel washes off lubrication in the cylinder walls causing heat in the ring lands. This leads to loss of seal letting oil in the chamber. Oil and nitrous aren’t good buddies. As I posted before I run a 32n 24f at 5lbs tune and it’s not too lean. There are local guys running 32n 32f at 6 lbs, then back it down to 5.5 lbs and bam swear they got it being lean, when really they got it on timing. My system is way leaner than that and motor is still living. I personally have never burnt a motor from being too lean, but once again I’m not saying it can’t be done. I do have pistons with lifted ring lands though. Hell there’s a guy around here that get at least one piston a week. It’s always some black magic voodoo problem that got his motor too. Everybody thinks he’s a god. “That’s what happens when you make power” haha. He cranks a bunch of timing in it to burn the fuel and melts her down. The question how fat is too fat is different to a lot of people. Personally I think if you can keep taking fuel away and your car doesn’t slow down then you’re too fat. The extra fuel is just beating your rings to death.

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Re: How fat is to fat

#18 Post by Deborah-WFO » Mon Jun 29, 2009 12:56 am

John_Heard wrote:Deborah - when you've seen pistons fail like that (ring land), do you typically see detonation evidence on the bearings also?
You would see some chatter or divots on the bearing. In the worst case the bearing would loose its press.

A big Nitrous motor will go through pistons as normal wear. Our motor lifts the ring land ever so slightly or bends the top ring a fraction. We pull the motor down after every race and look for this type of wear. We do not see it after every race, but we do every few races and replace a piston and top rings here and there.

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Re: How fat is to fat

#19 Post by soslojoe1970 » Mon Jun 29, 2009 4:13 pm

Just got an oxygen sensor set up with 2 sensors one in each header. What is a good a/f on motor and then on NOS? Going out to try it this weekend if anyone is racing on the 4th around here. Thanks...

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Re: How fat is to fat

#20 Post by 71Hellride » Mon Jun 29, 2009 7:51 pm

soslojoe1970 wrote:Just got an oxygen sensor set up with 2 sensors one in each header. What is a good a/f on motor and then on NOS? Going out to try it this weekend if anyone is racing on the 4th around here. Thanks...
I've seen guys have thier motors in the 13 to 1 range on the spray but i'd say at least 11 to 1 or 12 to1 range on motor and nitrous. Don't get hung up on trying to get that number, a lot of things can affect your ratio number i.e. exhaust leaks. Keep an eye on the plugs. You running a plate or a fogger?

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Re: How fat is to fat

#21 Post by Deborah-WFO » Wed Jul 01, 2009 12:16 am

soslojoe1970 wrote:Just got an oxygen sensor set up with 2 sensors one in each header. What is a good a/f on motor and then on NOS? Going out to try it this weekend if anyone is racing on the 4th around here. Thanks...

We do not use O2 sensors. I have seen guys get all hung up in that trying to tune with the O2. There is no substitute for reading the plugs that I have found in conjunction with being able to make tuning assumptions based on changing weather and your own knowledge of your engines behavior. I think the best thing you can do is track the data on the O2 and note when and under what other conditions the car runs best. Then observe the O2 as a factor of consideration in the mix.

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Re: How fat is to fat

#22 Post by soslojoe1970 » Wed Jul 01, 2009 6:52 am

FOGGER..... PRO-RACE NOS

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Re: How fat is to fat

#23 Post by John_Heard » Wed Jul 01, 2009 7:21 am

Deborah-WFO wrote: We do not use O2 sensors. I have seen guys get all hung up in that trying to tune with the O2. There is no substitute for reading the plugs that I have found in conjunction with being able to make tuning assumptions based on changing weather and your own knowledge of your engines behavior. I think the best thing you can do is track the data on the O2 and note when and under what other conditions the car runs best. Then observe the O2 as a factor of consideration in the mix.
Don't you wonder if you're leaving something on the table not knowing how the fuel curve changes during the run?

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Re: How fat is to fat

#24 Post by Deborah-WFO » Fri Jul 03, 2009 2:35 am

John_Heard wrote:
Deborah-WFO wrote:quote]

Don't you wonder if you're leaving something on the table not knowing how the fuel curve changes during the run?
I pick apart every piece of data we collect. Fuel Curve is something we don't really adjust for our application. In order of choice, I would select things for the chassis next. Like shock travel, ride height, and downforce on the wing. The fuel curve would be interesting to look at, but you would really need an O2 for each pipe. I look at each plug and adjust individual cylinder timing based on what I see and know about the engine's response to varied conditions. For me the O2 is kind of like trying to make critical tuning ajustments off of the EGT's. So lets say you are a little lean or a little rich in a certain spot in the run on a particular cylinder. Now What?

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Re: How fat is to fat

#25 Post by John_Heard » Fri Jul 03, 2009 6:21 am

Well let's take my car for example. I've only had O2 sensors on it for a few passes so far, but so far I have learned that it is consistently lean while the solenoids are progressing & the engine is also leaner on one bank than the other when coming up on the chip. At this point I'm assuming it's a carb issue that I need to figure out, my next thing I want to do once we get it put back together is make some motor only passes and look at the fuel curve. I want to see if adjusting the idle mixture screws on the lean bank help with tip in when going on the chip, and I want to see if that lean spot is there at launch also (no nitrous). I'll call the carb builder for suggestions if what I come up with doesn't work.

To answer your question, I would assume it's likely your lean at a certain spot in the run on one cylinder only I would want to look at other data to look for clues like EGT in that cyl - does the data correspond?. What else can you find? Is there a gasket leak on the intake port? Header gasket leak on that exhaust port? What's different about that cyl than the others? Spring pressure going down on that hole? Lobe problem? Leak it down is that hole got a problem? You know the drill, try and learn all you can and then make changes based on what you've learned. If I get stumped I start calling resources - whoever I can think of to lean some insight into what I'm fighting.

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Re: How fat is to fat

#26 Post by Deborah-WFO » Fri Jul 03, 2009 4:16 pm

John_Heard wrote:Well let's take my car for example. I've only had O2 sensors on it for a few passes so far, but so far I have learned that it is consistently lean while the solenoids are progressing & the engine is also leaner on one bank than the other when coming up on the chip. At this point I'm assuming it's a carb issue that I need to figure out, my next thing I want to do once we get it put back together is make some motor only passes and look at the fuel curve. I want to see if adjusting the idle mixture screws on the lean bank help with tip in when going on the chip, and I want to see if that lean spot is there at launch also (no nitrous). I'll call the carb builder for suggestions if what I come up with doesn't work.

To answer your question, I would assume it's likely your lean at a certain spot in the run on one cylinder only I would want to look at other data to look for clues like EGT in that cyl - does the data correspond?. What else can you find? Is there a gasket leak on the intake port? Header gasket leak on that exhaust port? What's different about that cyl than the others? Spring pressure going down on that hole? Lobe problem? Leak it down is that hole got a problem? You know the drill, try and learn all you can and then make changes based on what you've learned. If I get stumped I start calling resources - whoever I can think of to lean some insight into what I'm fighting.
No Doubt- Data is great!!!!
Here is where I would start with your issue. First, I have one of the countries best carb guys, Dale Cubic at Cubic Flow Modifications. He is very nice and would speak with you if you called. Our engines usually always see a right bank lean problem. I am staggering both the jet and the High Speed Air Bleed, meaning the lean bank has more fuel. Have you been able to observe your lean condition on the plugs? Certain cylinders are inherently lean due to the engines design. Certain cylinders will run leaner in different weather conditions at different tracks. For example, I have had problems with 5 and 8 in Fontana, but not in Las Vegas or Phoenix. The condition will change from morning to afternoon to evening. The most important thing is to look at your engine and don't become overly reliant on just looking at the computor to find problems. For example, you may not see a leaking header gasket on the computor, but if you will put a wrench on your header bolts and look each time for signs of a leak you will find it. You must also consider; What does your discovery really mean in the over all picture?

We went to the track one day with a friend. He went out in the morning a ran a record breaking pass. He comes back to the pit, never looks at his engine but changes his entire tune up based on the O2 readings. I looked at his plugs and told him the car was running on a perfect lean edge and that due to changes in the weather he may be a hair richer on the next run, but that he should leave it alone. But, No..., he can't do that. The next pass he can't repeat and he has trouble getting the car to go down.

The moral of the story is that you have to balance old school (Just look at your engine, plugs, run mechanical tests) with your computor readings, with reading the weather and track condition.

Now that you have discovered one bank is leaner that the other, how will you decide to put fuel in one bank or to take fuel out of the other bank? I assume you are running a progressor becasue you have a small tire and the progressor is giving the tire a chance to hook. What will be the effect at launch if you change the fuel curve? How will you correlate useful information from motor testing, when you are completely changing the condition when you turn the nitrous on? Test your theories though, its how we learn. 8-)

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Re: How fat is to fat

#27 Post by 71Hellride » Fri Jul 03, 2009 11:19 pm

soslojoe1970 wrote:FOGGER..... PRO-RACE NOS
With a fogger you can be a little sharper on the tune. The point I was trying to make is both ratios should be close. If your plugs are nice and clean and it reads upper 12’s I wouldn’t lose sleep over it. Monte runs a pro mod car way in the 13’s. It’s 800 c.i. spraying God knows what on it. In two years he has never hurt a piston or a ring.

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Re: How fat is to fat

#28 Post by John_Heard » Sat Jul 04, 2009 7:19 am

Deborah-WFO wrote: Now that you have discovered one bank is leaner that the other, how will you decide to put fuel in one bank or to take fuel out of the other bank? I assume you are running a progressor becasue you have a small tire and the progressor is giving the tire a chance to hook. What will be the effect at launch if you change the fuel curve? How will you correlate useful information from motor testing, when you are completely changing the condition when you turn the nitrous on? Test your theories though, its how we learn. 8-)
Yes, it is the right bank that is consistently leaner than the left coming up on the chip, but once the nitrous starts flowing that goes away quickly. Since that right bank shows a spike to 18, I'm pretty sure that side needs fuel in that situation vs taking it away from the left lol. Yes, we use multiple stages and a progressive to help soften things up on the small tire. Regarding the N/A testing, I want to get a baseline to see what's going on with the carb, I hardly ever run it motor only, so it's something that needs looked at.

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Re: How fat is to fat

#29 Post by Deborah-WFO » Sun Jul 05, 2009 9:53 pm

John_Heard wrote: Yes, it is the right bank that is consistently leaner than the left coming up on the chip, but once the nitrous starts flowing that goes away quickly. Since that right bank shows a spike to 18, I'm pretty sure that side needs fuel in that situation vs taking it away from the left lol. Yes, we use multiple stages and a progressive to help soften things up on the small tire. Regarding the N/A testing, I want to get a baseline to see what's going on with the carb, I hardly ever run it motor only, so it's something that needs looked at.

Let me know how your theory and tests turn out :smt001

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