FrontEngineDragsters.Org Forum
Technical => Spud Miller's Cave => Topic started by: masracingtd1167 on October 28, 2019, 01:05:34 PM
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A little disappointed in the performance of my car this year ! After getting my tire problems straightened out I thought I could get my car to run in the six's ! Went from 15 percent to 20 and then 25 and no real gains at all ! Plugs look great and the motor seems happy ! The car runs the same MPH on nitro as it dose on straight alky ! It seems like the motor is falling off at 9400 and it used to pull good to 9700 ! Valve springs are fine ! I still have the same gear and converter that I used on alky and the converter is on the loose side it stalls at 8200 ! Wondering if a tighter converter would help! Just kind of lost and looking for some advice !
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I do think the Nitro gains would be at lower RPM and tighter stall may help with that. With your motor turning lower RPM than it was before I suspect something else may be going on. What kind of injection you have?
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What jetting/ timing changes did you make for 25% if any?
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Over the winter I did drop the compression from 14.5 to 12 to 1 and I also went to a 14 lbs oil ring from 11 lbs and a tool steel top ring from a gapless ! Jetting from a 88 jet on alky to an 84 with the 25 percent !
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Such a low percentage is only going to give you stink and very little gain
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Such a low percentage is only going to give you stink and very little gain
Bruce The car did pick up the year before when we first tried the nitro at 13 percent but that was at the higher compression ! With the 13 percent it went from 4.60 eighth and high 7.20's at 181 to 4.51 eighth 7.11 at 186 ! Right now with the 25 percent it will still run 4.51 to the eighth but just seems to fall off after and only run at best 181 ! I have been wondering if my ignition might not be putting out enough ! would a 25 percent mix be harder to light ? My MSD 7AL3 box is getting old 12 years and if I have to buy a new box I think I might just go ahead and buy a Mag ! Plug wires are also 12 years old so I think it is time for some new ones I guess I got my money's worth out of them !Going to send my fuel system to Spud and have it flowed ! Any other ideas Guy's !
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More timing with more Nitro ?
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More timing with more Nitro ?
I know nothing but I think at 25% you treat it as an alky engine still.
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After reading the 51 part youtube documentary on The Surfers TF team of the 60's I remember that teams were having hi-rpm problems because of the mag kill switches they were using. They installed a knife switch on the primary side of the mag to cure the problem. This may-or-may-not be relevant with an MSD but I would look at it nonetheless.
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I did try more timing went from 34 to 36 and showed nothing yet the plugs look like it could use more !
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what did added percentage do to converter stall? Thinking you probably picked up 400 rpm on stall. I know you read spuds nitro notes dozen times. He did say you would probably end up little leaner when at ideal jet..Since you have the compression down throw some more nitro at it. If pump can handle it you will probably need little more nozzle if going over 30%. I was told about 600 to 700 change with tq change if running 30%,based on spud's nitro tq calculator. With less compression you might be able to bump ignition.Speaking of which. Are you sure its up to task if increasing %?
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The problem with electronic ign is that the duration is not long enough for Nitro/Alc. Elec ign fires a precise spark at XX deg's every single time and with gas, that is what you want, but alc/nitro makes power at different times during combustion. When the engine is cold the mix fires with the piston close to the top of the stroke with the static compression, as the engine heats up the mixture fires sooner and if you add boost to that even earlier, so with that you need a spark that covers that range for which a magneto provides. Lighting the mix early than full boost and/or heat require, you are running out of juice early on when things are not optimum to making the power. Making power in the beginning of the pass really knocks the ET down more than the gain on the top. If magnetos didn't work, they would use something else, Personaly ,would not run a mag with gasoline, that's where the electronic shows its strenght
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33% and under my alcohol tune up and nitro tune ups were the same. My experience is the more nitro the greater effect on the converter. In my case I slowed down the more % I added.
Mark S
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Thinking over the ignition part of it going to test my box ! Going to change converter for sure and send the fuel system out to be tested ! My season is over here in the north east so I will just have to wait till spring to test again ! Took the heads off last night and the cylinder walls look great !
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Over the winter I did drop the compression from 14.5 to 12 to 1 and I also went to a 14 lbs oil ring from 11 lbs and a tool steel top ring from a gapless ! Jetting from a 88 jet on alky to an 84 with the 25 percent !
The drop in compression may be a reason for the drop in power also? 12-1 and 25% may be similar results as your 14.5-1 and 15% maybe
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Thanks for all of the advice guy's ! I guess I will move forward from here and make what I have work ! I was talking to a friend of mine who runs a comp car with a blown small block and they were having a problem with a high speed mis fire and he tried a mag and picked up big time so I think that might be my solution as well ! My sheet metal intake has no room for a mag so I might have to use an off set drive or go to a cam drive !
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My solution to intake / mag interference. Two Boston HLK-101Y bevel gears in a custom gear box.
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Bill call Mr Parks he has a trick piece that drives mag,fuel pump and I believe a vacuum pump if you are running one.
You mean you can run a FED w/o a mag? Hum I thought that was just standard issue.LOL
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Bill call Mr Parks he has a trick piece that drives mag,fuel pump and I believe a vacuum pump if you are running one.
You mean you can run a FED w/o a mag? Hum I thought that was just standard issue.LOL
I have an RCD tri-drive in the spare parts closet I ran a mag, fuel pump, and an System One oil pump with it
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Bill, your setup an mine are day and night different (blown hemi with direct drive), but I'll share what I have learned. I also started with low % nitro and pretty quickly worked up to 40-50%. ET gains came with each jump in %, but the MPH gains were more significant.
When I moved from the 7.50 class to 7.0, I increased to 70-75% and added a bunch of clutch to it. To make more power you have to have more fuel, more fuel wants more clutch, more clutch wants even more fuel, and more fuel wants more spark energy. It all has to play in the same sandbox. Somebody mentioned your convertor and for sure, you will want it tighter for fuel.
My best tuning aid was when I took off my mag IV and put on an old Schiffer-Cirello unit for looks. It would put raw fuel out the rich cylinders and I was able to balance the fuel system much better. When I got to higher % I had to go to a mag V to keep the holes lit. I have a mag + that I'll likely switch to.
I also see a drop in ET if it's tool long between the warm-up and a race and the cylinder head temps drop too much.
My opinion is that it's much easier to run nitro with a blower, but the injected guys might have a different opinion. Just be sure to pull your plugs and clean out the chambers and lines before trying to start it. Also, if you have gas ports in your pistons I have heard of a case where they caused an issue with nitro.
Steve K.
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So if my ignition is weak will it just not burn all of the fuel ? I did notice the last time out that it was spitting some raw fuel out of the pipes ! Can this cause other problems like detonation !
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Without going overboard, you cant have too many amps with nitro. A friend was trying to run blown nitro in an altered exhibsion class and a vertex, not enough spark to burn/light the fuel , leaned it down and burned up the engine. Times were in the low 8 high 7's
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I think that's where I am right now with this and I do plan on switching to a mag for next year and up dating the fuel system !