Why won't my car do a burn out from a standing start

[RocketcarX]

So I gave up tuning my car fro now and handed it over to Lito. So far we are making progress...slowly.
In my mind I should be able to stomp the loud pedal and at least spin the tires a little.
I have 4.30 gears and a FTI 9.5 inch converter with a 3800 rpm stall (4r70W swap)
The power comes on like a 2 stroke, slow to get rolling and then just GOES!
I realize the cams (mutha thumpr 127020) play a role in this power curve but the gears and converter should be taking car of that low end deficiency. Before you start bagging on the cams as a the problem here, I have had plenty of "built" cars with less power and smaller converters with taller gears that could roast the tires on command. My last street truck with a shitty B cam in a small block 306 and 10" ATI 3400 stall converter comes to mind, and that truck had a tiny 600CFM vacuum secondary carb on it with a very basic HEI ignition system I didn't even tune the curve on.
If i don't use the line lock she ain't spinning tires, it's embarrassing.
To be honest I'm getting sick of constantly messing with this car and it always being out of whack, I just want to start racing and it's feeling like a huge waste of time and money to constantly be in this state of purgatory.
I haven't even sprayed it yet, I have this mega dollar Nitrous Outlet system complete with the ProMax and all I've done is hit the purge...shit is depressing.

 

[01yellerCobra]

Maybe Lito is sneaking up on the final set up.
I'd imagine your car hooks up a little better than a truck with just a bed over the tires as well. I'd run it at the track personally. It might not hit your goal but you might still have fun.

 

[RocketcarX]

Maybe Lito is sneaking up on the final set up.
I'd imagine your car hooks up a little better than a truck with just a bed over the tires as well. I'd run it at the track personally. It might not hit your goal but you might still have fun.

I'm sure it will be fast, and over the winter I'll build the bottom end so I can spray the piss out of it. I just feel like it is soft out of the hole, even on street tires it wouldn't turn them hard enough to spin them.
When the car was a stick shift it was not problem and I didn't need 3800RPM to do it, lol. I guess I'm like one of my customers who spends a certain amount of money and doesn't like the results, haha. Like dammit, I paid all this money for this! I have a small fortune in this car at this point, and none of it is in labor, lol.
I know we'll get there, I'm just ready to be doing the damn thing instead of always working toward this ever fleeting goal.

 

[kazman59]

Too much traction, or not enough power...

 

[skwerl]

My Bullitt bogged off the line every single time, really hurt my 60' times. That's why I was only running 10.5 in the quarter at 138mph. I never did get it ironed out.

 

[Sky Render]

Put some 235 all-season tires on the back. You'll spin 'em every time!

 

[01yellerCobra]

I'm sure it will be fast, and over the winter I'll build the bottom end so I can spray the piss out of it. I just feel like it is soft out of the hole, even on street tires it wouldn't turn them hard enough to spin them.
When the car was a stick shift it was not problem and I didn't need 3800RPM to do it, lol. I guess I'm like one of my customers who spends a certain amount of money and doesn't like the results, haha. Like dammit, I paid all this money for this! I have a small fortune in this car at this point, and none of it is in labor, lol.
I know we'll get there, I'm just ready to be doing the damn thing instead of always working toward this ever fleeting goal.

I get it. I was there with my last car. It was always "one more thing and it'll be done". But the times it did run it ran like a bat of hell.

 

[eighty6gt]

I am working on getting an S197 front cut so I can develop my engine mounts and headers for the LS swap into this platform, should solve all of these issues.

 

[46addict]

Why an LS? If you're doing custom fabbing why not make a SBF stroker fit?

 

[eighty6gt]

wayyyy too expensive to reliably make the same power. The junkyards and ebay aren't full of 500-600 hp capable sbf strokers.

Also, once I get some measurements, I believe the common LS T56 should be a great match for these cars. Instead of paying $6000 for a magnum xl, you can use a junkyard unit and my crossmember and brand x drive shaft.

 

[Flusher]

I have some thoughts, but they are purely based on my experience with older Chevy and Mopar engines. Also, I have spent only a little time researching these engines, so I have nowhere near the expertise that I have with old engines. Nonetheless certain concepts carry over.

Not trying to bag on your cams, just thinking here:

CompCams describes the Mutha Thumpr cams as "...Great power above 4900 rpm. Compatible with stock valve springs, benefits from converter & gears, requires cam phaser upgrade & custom tuning" (http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1434&sb=2).

The CompCams cam phaser limiter kit "restrict the range of cam timing movement to only 20 degrees" compared to the OE cam phasers "...ability to retard the cams up to 60 crank degrees" (http://www.compperformancegroupstor...c?Store_Code=CC&Screen=PROD&Product_Code=5449).

In the world of oldschool pushrod engines, 60-degrees is frakkin HUGE! Cams would most commonly be installed at 4-degrees advanced with around 10-degrees advance or retard being common in select timing sets. Maybe I'm not thinking broad enough a need push my limits more.

Cams are typically installed 4-degrees advanced because that is where the average build achieves the best average power in the RPM range. Advancing the cam starts airflow into the cylinders earlier and builds more cylinder pressure because of the earlier intake valve closing. This has the effect of rocking the power curve about peak torque, favoring low-end. Retarding the cam timing has the opposite effect of favoring the top-end. The intake valve is open later during the intake cycle, giving the cylinders more time to fill at high RPM.

Some issues arise in the old pushrod engines that I don't see how they could not also exist in the SOHC/DOHC engines. As the valve timing is advanced, intake valve to piston clearance reduces. Retarding reduces exhaust valve to piston clearance.

Increasing the lobe duration, for any given centerline, has the same effect. More interference on intake opening and exhaust closing.

CompCams cam phasers limit cam timing by 2/3 and without measuring everything (or calling CompCams tech support), I have no idea where timing is being taken away. Looking at pictures of pistons and combustion chambers, I suspect that timing is limited at both ends. However, based on all of the camshafts that I have measured, the advance/intake side needs to be limited more than the exhaust side, but that is speculation without knowing the chamber and dome shape or if the valve notches are designed properly.

I think that there might be gains to be had from optimizing piston dome shape and valve notches, followed by optimizing cam phaser range.

Next, I have noticed that piston selection for the modern engines is pretty weak. Seems like there are only two compression ratios to choose from and decking the block/heads is not an option.

In dealing with oldschool, compression limited engines, compression plays a huge roll in how an engine feels to drive and the power it will make. Increasing duration on an already low static compression ratio engine will kill the dynamic compression ratio. Other mods such as large intake manifold and exhaust will further reduce the actual compression ratio that the engine sees while running. All of this adds up to the car falling on its face when you mash it. I'm sure you have heard the saying, "it's all about the combination."

The following is pure speculation and possibly just a rant on the modern vehicle's electronics: I am not a fan (yet) of TCS and especially the fly-by-wire throttle. That combined with the aftermarket cam phasers, I think a software problem is a contributing player, but I am far from an expert in that area (for now).

Good luck,

Joe

 

[skaarlaj]

Loosen up your stall. Maybe get to a dyno, and see at what rpm you engine starts making good steam, than tell the stall/converter manufacturer. Before I had my 5C on my 2011, it would not spin street tires from a dig at the track or on the street. The car still felt powerful, just not off the line. After the converter, I could rip my QTP's at will. I know you already have an aftermarket converter, but maybe it just isn't loose enough.

 

[RocketcarX]

Too much traction, or not enough power...

Both of these apply, I'm sure

I am working on getting an S197 front cut so I can develop my engine mounts and headers for the LS swap into this platform, should solve all of these issues.

No, fuck an LS

I have some thoughts, but they are purely based on my experience with older Chevy and Mopar engines. Also, I have spent only a little time researching these engines, so I have nowhere near the expertise that I have with old engines. Nonetheless certain concepts carry over.

Not trying to bag on your cams, just thinking here:

CompCams describes the Mutha Thumpr cams as "...Great power above 4900 rpm. Compatible with stock valve springs, benefits from converter & gears, requires cam phaser upgrade & custom tuning" (http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=1434&sb=2).

The CompCams cam phaser limiter kit "restrict the range of cam timing movement to only 20 degrees" compared to the OE cam phasers "...ability to retard the cams up to 60 crank degrees" (http://www.compperformancegroupstor...c?Store_Code=CC&Screen=PROD&Product_Code=5449).

In the world of oldschool pushrod engines, 60-degrees is frakkin HUGE! Cams would most commonly be installed at 4-degrees advanced with around 10-degrees advance or retard being common in select timing sets. Maybe I'm not thinking broad enough a need push my limits more.

Cams are typically installed 4-degrees advanced because that is where the average build achieves the best average power in the RPM range. Advancing the cam starts airflow into the cylinders earlier and builds more cylinder pressure because of the earlier intake valve closing. This has the effect of rocking the power curve about peak torque, favoring low-end. Retarding the cam timing has the opposite effect of favoring the top-end. The intake valve is open later during the intake cycle, giving the cylinders more time to fill at high RPM.

Some issues arise in the old pushrod engines that I don't see how they could not also exist in the SOHC/DOHC engines. As the valve timing is advanced, intake valve to piston clearance reduces. Retarding reduces exhaust valve to piston clearance.

Increasing the lobe duration, for any given centerline, has the same effect. More interference on intake opening and exhaust closing.

CompCams cam phasers limit cam timing by 2/3 and without measuring everything (or calling CompCams tech support), I have no idea where timing is being taken away. Looking at pictures of pistons and combustion chambers, I suspect that timing is limited at both ends. However, based on all of the camshafts that I have measured, the advance/intake side needs to be limited more than the exhaust side, but that is speculation without knowing the chamber and dome shape or if the valve notches are designed properly.

I think that there might be gains to be had from optimizing piston dome shape and valve notches, followed by optimizing cam phaser range.

Next, I have noticed that piston selection for the modern engines is pretty weak. Seems like there are only two compression ratios to choose from and decking the block/heads is not an option.

In dealing with oldschool, compression limited engines, compression plays a huge roll in how an engine feels to drive and the power it will make. Increasing duration on an already low static compression ratio engine will kill the dynamic compression ratio. Other mods such as large intake manifold and exhaust will further reduce the actual compression ratio that the engine sees while running. All of this adds up to the car falling on its face when you mash it. I'm sure you have heard the saying, "it's all about the combination."

The following is pure speculation and possibly just a rant on the modern vehicle's electronics: I am not a fan (yet) of TCS and especially the fly-by-wire throttle. That combined with the aftermarket cam phasers, I think a software problem is a contributing player, but I am far from an expert in that area (for now).

Good luck,

Joe

Judging by the design of the limiters I think they limit one side of the equation, not sure which. You're right, the car needs more compression for sure, and the tune is still a work in progress

Loosen up your stall. Maybe get to a dyno, and see at what rpm you engine starts making good steam, than tell the stall/converter manufacturer. Before I had my 5C on my 2011, it would not spin street tires from a dig at the track or on the street. The car still felt powerful, just not off the line. After the converter, I could rip my QTP's at will. I know you already have an aftermarket converter, but maybe it just isn't loose enough.

This has been on my mind a lot, I'm going to pull the converter and have it re-stalled ASAP, I get 1 for free within the 1st year of ownership. I think I need the "hard hit" option offered by FTI instead of the tighter version 3800 I have now. It will stall to the quoted RPM but I need it to do it off the line, and hit the tires HARD.