87silverbullet

iTrader: (11)

Martin, you think there is more load on a motor going into 3rd gear at high rpm compared to launching a car out the hole in 1st?

I know there is multiplication with the gears and all but I would think trying to move the weight from a dead would be more load and at such a lower rpm.

speedtigger

iTrader: (16)

I think there is the most chance for detination on the 1-2 shift also. There is typically a larger gear spread from 1-2 than 2-3 and, on the shift, the engine is at max VE top of first when it hits 2nd there is a moment of extra high VE. I used to see this present itself on my turbo Buicks big time.

Also on the top end going through the traps with wind resistance and sustained high Rpm is a lot of load also.

shortdog

iTrader: (1)

More like 400 rwhp worth

Sales@Tick

iTrader: (3)

I would say that on the bottom of the shift extension going into high gear is where maximum load occurs.

Depending on the gear ratio's used as Speedtigger mentioned it may happen in 1-2 as the 200R4 that a GN uses has a 2.74 first and a 1.57 second where as a Th400 has a 2.48 first and a 1.48 second which is less of a drop. I would still say gear spread set aside that maximum load occurs in high gear as that is where the engine is straining the most against load incurred by the drive train and track itself due to the gear ratio.

Most engines that are going to let go like this do it in high gear towards the end of the track not off the line mainly because of load. The highest amount of heat is put into the cylinder in high gear further down track due to load.

87silverbullet

iTrader: (11)

Well, off the line the heat hasn't built up yet. With that said I would think there would be more of a strain out of the hole with trying to move weight from a dead.

Think about it. Cam was on the bottle out of the hole so, yes there was heat building up and the 2-3 shift on the bottle with weight killed the motor.

Now lets say he ran it on the motor until he shifted into 3rd then hit it. Do you think he would have blown it up? I don't think it would have due to not having the heat build up.

Sales@Tick

iTrader: (3)

I agree, that of course he wouldn't of blown it up because there was only a short duration of higher cylinder pressure. It wasn't under sustained load all the way down track and didn't make enough heat energy to do the damage it did.

Still that doesn't mean that maximum load isn't seen in high gear. Out of the hole the converter hasn't even fully coupled yet until 40'-60' out and even with that the gear reduction hasn't produced enough load to match the loads seen in high gear. I guarantee an engine uses the most lbs. per hour of fuel at the bottom of the shift extension in high gear because of load and it will taper off as the rpm's climb. It's the same reason a turbo motor will make more boost on the gear shift than at the top of 1st or 2nd because maximum load is seen there due to reduced gear reduction.

There is more mass to an object when it is traveling at higher speeds which creates more load especially when the motor is being forced to strain more with reduced gear ratio. The reason a motor revs easier in 1st and 2nd as it goes down the track is because of less load due to less total mass being moved and because more gear reduction allows it to move easier. Less rolling resistance at low speed is going to create less load. Also as Speed Tigger said wind speed pressing against the vehicle will rise as mph rises also so more resistance will be created then.

Anyways, I guess we can agree to disagree.

camscam02

iTrader: (21)

Yup all of that is correct. Not many should try to duplicate it though. Be careful. As far as the culprite the longer the pass the more heat and cylinder pressure there is. It's all about time

minytrker

iTrader: (13)

Its all about borrowed time when your running stock bottom ends and pushing the envelope. I have ran 3 stages before, a 57 jet, and 2 70 jets on a few 1/8th miles passes on a stock 6.0. in my old truck. I had all 3 on by the 60ft. I ended up backing it back down to 2 70 jets and it liked that better. It defiantly wouldnt have made it through the 1/4 on all that.
The tune has to be spot on also with alot of nitrous. Its still crazy how much abuse ls motors will take. How many miles were on your motor?

87silverbullet

iTrader: (11)

I'm not disagreeing with you at all Martin, just trying to learn.

I went to GM ASEP school and learned alot but that only takes you so far on learning the Gm stuff on a stock scale.

I know this doesn't relate too much but its close ,this is what I'm basing this off of. When I was in GM school I did valet for a hotel. I used to drive Cadillac DTS's with 4.6 northstars on 87 octane that were rental cars. When you would punch it from a dead you could immediately send the car into knock retard right off the line due to the load and the PCM couldn't pull the timing out enough to stop the valves from clattering. At 5000+ rpm though is the only other time the same condition would occur. (Don't ask me why we were taching these cars up over 5000 rpm) It wouldn't be as severe though.

I'm seeing it as so much timing would need to be pulled to take the hit at the line due to so much load and less at the top end due to less load. So in turn more strain at the line compared to 3rd gear.

You say that there is more mass at speed causing strain but, that mass is rolling at that point. If the mass is not moving, the weight of it causes strain.

I understand all the variables in what goes on at the top of the track with wind resistance and less gear multiplication. I just trying to point out what goes on at the other end of the track with moving a 3500lb car from a dead stop.

When you tune a nitrous car at the track do you spray in the front half then shut it down or do you spray in the 2nd half then shut it down?

Sales@Tick

iTrader: (3)

It's really simple and all comes down to gear reduction and converter efficiency.

Put your car in 1st gear and floor it from a dead stop, notice what it does.

Now put your car in 3rd gear and floor it from a dead stop and notice what it does.

In 1st gear it will move much easier because of more gear reduction and because the converter isn't locked up yet and allows for slip.

In 3rd gear it doesn't want to move and has much more strain on it because the loss in gear reduction makes it much harder to move that mass. This then loads the motor much more than having more gear.

Down track the converter is locked up and has much less slip than off the line causing more load and strain. More slip and more gear reduction makes the car easier to move and if it's easier to move there will be less load.

This is why you don't run it out the back door of the track on an un-known tune-up because of how much more load is created in high gear which can wreak all kinds of havoc on a motor if the tune isn't correct. It has less of a chance of doing it in the lower gears because of less load and heat created because of that.

This is also why I can run much more timing in 1st gear off the line than I can down track when I'm spraying and not see knock or peppering on my plugs. There is less load on the motor so I can use more timing to create more cylinder pressure. I'm basically making up for the loss in cylinder pressure with timing in 1st gear that would be seen with less timing in 3rd gear with more load due to mass and gear reduction along with the converter being locked up.

NitrousExpress

iTrader: (4)

Man Cam sorry to hear that you broke but you have defiantly given it hell. Are you planning on staying with a stock bottom end motor or are you going to something bigger?

Trey

camscam02

iTrader: (21)

You have it spot on. Just missed it by a bit and with that much nitrous it was time. My motor has 36K on it. Probably 150 or so nitrous passes and 200 or more NA passes on the conservative side.

Thanks man. It was a fun ride. Im not exactly sure what were gonna do yet. We want to be ready by mid November so we can get to the SCSN in Vegas. We want to throw together a 402 in the next month and get it in, but may just fix mine real fast to get back out there. So many options...

speedtigger

iTrader: (16)

Be sure to post up the carnage after the tear down.

dnkynrbk

iTrader: (34)

great job on getting the numbers sorry to hear about the motor.

NitrousExpress

iTrader: (4)

Well looking forward to whatever you are going to do.

Agreed I would defiantly be in for pics.

Trey

camscam02

iTrader: (21)

Motor is almost out of the car and I should have pics for everyone in the next couple days.

The possible plan at this moment is to put new forged pistons, rings, bearings in it and rod bolts why we are there. Hopefully gonna up the compression a couple points depending on what piston we use and also a possible cam change to take better advantage of how much nitrous we are using.

Ill keep everyone updated but it should be back together relatively soon

Justins00ss

iTrader: (18)

Good to hear Cam. Kinda in the same boat. My stock bottom end just spun a bearing on Saturday. Not to sure what to do with it. Forge it or build it bigger.

Sales@Tick

iTrader: (3)

Remember what I said, if you need a new cam profile let me know.

I've got an off the shelf nitrous cam that is 238/252 .615/.595 114+5 that would work great for you cam.

StrokerTA

Martin what does your car run to the 1/8th on HP?

Sales@Tick

iTrader: (3)

It went 6.40's@104.5 on motor with the N/A stall and 7.01@98 on the previous nitrous converter with the old stator in it that it had on the first nitrous re-stall(I'm on the second nitrous re-stall now)

I think I found another reason why I never ran the times I thought it was capable of and that was with the old stall on the chassis dyno it looked like the torque was peaking at 5700-5800 rpm when in all reality it probably wasn't any higher than 5000-5200 as the new dyno graphs show.

I told FTI I wanted the stall to flash to 5800 on nitrous.... well I was missing peak torque by a good 600-800rpm by doing that so I told them I wanted it to flash to 5200-5300rpm on nitrous this time. It's flashing to 4800rpm on motor which has me kind of worried that it's still going to flash too high but it will only go 4200-4300rpm on the transbrake now with no two step rpm limiter set whereas it would go 4800-4900 on the first nitrous re-stall I had done.

I've heard of people using tight nitrous stalls before on YB that thought the stall would be too loose by judging what it stalled to on motor on the trans brake because it was within 400-600rpm of what they wanted it to stall on a large amount of nitrous, but when the time came to spray, it was dead on what they wanted. I hope it works out that way for me too.