Mike or Eugene from Bode's car: start up procedures of a nitro engine

[flapjack]

I know the second spin of the starter is for actual firing of the engine, but what
is the first spin for? I've heard it is to bring oil pressure up, but I've also heard
it is to clear the chambers of nitro to prevent a subsequent boom on the
second spin. But if there was nitro in the chambers to begin with, one would
think there would be a boomer on the first spin.

What gives?

 

[big guy]

I am not Mike or Uegene,butthe staring procedure is as follows
Warm up procedure
1 Back it down to rid all the cylinders of nitro,or any fuel.
2 Roll for oil preassure
3 prime the hat
4 Fire up on one mag and let it die ( to ckeck that mag)
5 Back it down again
6 Prime the hat again
7 Fire up om the second mag,pull the first mag wire.
8 Go to nitro

 

[flapjack]

This is what I was looking for, mainly, the first spin is NOT for clearing the engine. But I still don't understand how you can back down an engine and not explode nitro as one will there will be compression at some point of backing down.

I feel stupid.

 

[clock guy]

the Mags are grounded out when you do this. No spark no boom

 

[twostep]

the Mags are grounded out when you do this. No spark no boom

I think he means is combustion possible VIA compression only (dieseling). At that slow speed (backing down process), I wouldn't think so but I can't say for certain.

 

[Toejam]

Did anybody hear what caused the Boomer Scott Weis had at Indy a few years ago?

 

[big guy]

Did anybody hear what caused the Boomer Scott Weis had at Indy a few years ago?

Not exactly sure,but I think it was not backed down and had some nitro in one hole.

 

[You!]

the Mags are grounded out when you do this. No spark no boom

Wow...that statement really couldn't be more incorrect.

 

[.]

Did anybody hear what caused the Boomer Scott Weis had at Indy a few years ago?

I read somewhere that nitro had puddled inside the blower (small amount) and when they spun it over it banged.

 

[Kansas Stan]

To hydraulic a motor, you don't have to have fire. If fuel is present in sufficient quantity (and it don't take much) rods will take the path of least resistence when the motor is spun over. The cylinder doesn't know the difference between liquid and billet steel....when there's no room, there's no room, period.

 

[Guppy]

Also, When you back it down, It is rotated backwards. fuel OFF, mags grounded.

 

[flapjack]

Also, When you back it down, It is rotated backwards. fuel OFF, mags grounded.

But my question remains: when you back it down, there will eventually be
a point when fuel in a cylinder is compressed. that's not good. What about
backing it down makes this particular type of compression better?

 

[d'kid]

lack of speed, like maybe 1 to 2 rpm

 

[Muddy]

When you rotate it backward there is no compression stroke and there is generally enough overlap in the cam to avoid compression anywhere else.

 

[Huge]

Tom we have a routine that we follow every time we warm up. We back the motor down before we fire it to get any nitro out of the cylinders. Backing it down turns the cam shaft the opposite direction so the valves open and close with no compression stroke and any fuel will be forced out in to the headers. About two and a half revolutions of the crank shaft should do it. The compression makes nitro unstable and therefore detonates it. That is why nitro comes in a thin walled drum, so if it builds heat and becomes pressurized it can expand the wall of the drum. The spark makes it easier to detonate. Our next step is to spin the motor over and run it on gas out of the squirt bottle for a few seconds. This does help build oil pressure and it lets us see if every thing is ok. Then Mike [aka Uncle Fester] spins it over and lights one mag and then the other mag on nitro. We don't warm up on alky like some of the teams do. Then Wally checks the timing and sets the idle and goes through some other functions. We spin the tires both ways to make sure the reverser is working and that we don't have any broken axles. With the levers we have on the car now, we don't whack the throttle to seat the clutch. Then Wally pulls the fuel line off and runs it out of fuel to kill the motor. I hope this has been helpful to you. Remember that all teams have there own routine.

 

[twostep]

Thanks, Eugene. Learned a few things here.

 

[flapjack]

Thanks, Eugene.

 

[Buns]

Thanks, Eugene. Learned a few things here.

+1 Thanks for the info!