SPT 8200rpm Gen 4 dry sump engines

[Dan Cragin]

We just finished another ACRX race motor and were able to correct some valvetrain issues we have had on the production ACRX build, as well as find the HP limit of these motors with the Mopar VVT cam.

In the past, we have had lifter and camshaft failures, in as little as 1 season. If these engines are run consistently between 5500 and 6500 rpm in race conditions, they experience valve float and can damage the lifters and cam.

The VVT system on the Gen 4-5 engine is limited by valve spring pressure. Too much pressure and the VVT will not function properly, too little and they go into valve float.

In order to run more spring pressure and still use the VVT system we made some major modifications to the valvetrain and heads. This included custom short travel lifters, stronger pushrods, lighter valves and shaft mounted rocker arms. The bottom end was built to motorsports specification with a nitrated crankshaft, better rods, pistons and bearings. The end result was an engine that will rev to 8200rpm without any durability issues.

We added a dry sump system to reduce windage, increase oil volume and give us the ability to adjust the oil pressure perfectly for the VVT system.
We did quite a bit of work to the heads, adding beryllium valve seats for heat transfer and extensive porting. It turns out that there are limited gains from porting with the stock camshaft, the stock heads can support 800hp, but with porting we can get more power, even with the stock VVT. Raising the compression for race fuel only, we hit the hp wall at 715hp with the stock VVT cam. We could run more lift and much more compression, but without a cam profile change I would doubt we will see more than 20hp. In the future we plan to regrind the VVT cam for more power or go with a single profile VVT delete cam for big numbers. Sticking with a modified VVT is really neat project for a track car as the this cam gives a really smooth torque curve without the big dip around 4-5000rpm, which we see on all the single profile cams.

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Torque output from a VVT cam from 1000 to 3000 rpm beats anything a single profile can do, with a modified VVT profile torque could be optimized through a 8000 rpm range, that's a really wide power band!!

I hope this is interesting to those thinking of making Gen 4-5 modifications or building a competition engine.

[TwinVipers]

Very nice! Can you post some dyno graphs showing the tq curve up to 8000rpm? Also, who made the dry sump set up? Thanks!

[Nine Ball]

Thanks for sharing, and doing the experimenting. Any vids of the engine at max RPM? What does it sound like?

Tony

[BAD BOYZZ GARAGE]

@8200 rpm I'm subscribed..

[Steve M]

Thanks for sharing, and doing the experimenting. Any vids of the engine at max RPM? What does it sound like?

Tony

I would guess a very angry UPS truck...perhaps one that was running late around Christmas time.

[FLATOUT]

So cool!

[XSnake]

Damn!

[slowhatch]

This is amazing. What were you using to control the VVT system (tuning)? Im guessing the hp figures quoted were from an engine dyno?

[IndyRon]

Dan, thanks for sharing this information. Can you elaborate on a comment you made regarding oil pressure and the effects it has on the VVT setup? I'm curious about how this system functions in regards to RPM and oil pressure.

How cool would it be to have a complete top end package consisting of ported heads matched to a nice healthy but driveable street grind VVT cam setup and the associated valvetrain parts and make 700rwhp NA. I would think that even without the dry sump, 7k rpm would be attainable with the proper valvetrain on stock shortblock, right? Thinking out loud, the stock Gen 5 intake is done over about 6000rpm though so some work would likely be needed there.

[FLATOUT]

That would be one of the most impressive NA builds to ever hit the streets :D That being said I bet it will be exspensive as Fug.



Dan, thanks for sharing this information. Can you elaborate on a comment you made regarding oil pressure and the effects it has on the VVT setup? I'm curious about how this system functions in regards to RPM and oil pressure.

How cool would it be to have a complete top end package consisting of ported heads matched to a nice healthy but driveable street grind VVT cam setup and the associated valvetrain parts and make 700rwhp NA. I would think that even without the dry sump, 7k rpm would be attainable with the proper valvetrain on stock shortblock, right? Thinking out loud, the stock Gen 5 intake is done over about 6000rpm though so some work would likely be needed there.

[SlateEd]

Thanks for sharing, and doing the experimenting. Any vids of the engine at max RPM? What does it sound like?

Tony


+1 - that must sound incredible

[Derek Short]

I would guess a very angry UPS truck...perhaps one that was running late around Christmas time.

This made me lol.

[IndyRon]

That would be one of the most impressive NA builds to ever hit the streets :D That being said I bet it will be exspensive as Fug.

Probably right about both points....I'm thinking parts plus labor/tuning at less than 10k turn-key would make it really enticing for many gen 4/5 guys. I don't know if that's even in the ballpark though.

[FLATOUT]

I agree, these things would haul the mail at that power level especially if we lighten them up a 100lbs or so.


Probably right about both points....I'm thinking parts plus labor/tuning at less than 10k turn-key would make it really enticing for many gen 4/5 guys. I don't know if that's even in the ballpark though.

[V10LEE]

Dan that is amazing! You guys are the best there is when it comes to Vipers.. Wow..

[mjorgensen]

Dan that is amazing! You guys are the best there is when it comes to Vipers.. Wow..


+100 ^^^^^^

[Dan Cragin]

Thanks for the comments, we cant wait to get this car on the track. Yes, the HP numbers were on the engine dyno. I will see if I can post up the dyno graph. I did not video the engine but will next time. We wont be running this engine over 7200rpm on the track, as it does not make any more power up there because of the cam. We ran it that high on the engine dyno to confirm we had resolved all the valve float issues. Once we get a bigger VVT cam we can get more usable rpm. With the Gen 5 cam and manifold it most likely would have made more power on the top end.

The dry sump is made by Dailey, same as the GTSR setup. In regards to VVT and oil pressure, if you run more valvespring pressure, you can overcome the hydraulic function of the VVT, with a dry sump, you can change how fast the pump runs and taylor relief springs to get the oil pressure where it needs to for the VVT.

The G4-5 engines do not suffer from the oiling issues like the earlier engines, so they like rpm. The crankshaft driven front pump has its limitations but 7000rpm should be fine.

We will be doing another build soon, just as soon as we determine what to do with the camshaft.

[Magnus]

Great work.

I like to see these kind of builds. I spin my gen4 race motor to 6750 all weekend long.

I wonder if I'll be racing against this motor at some point. :D

- Keith@HPTuners

[ACRucrazy]

I <3 this thread.

[slowhatch]

I spin my gen4 race motor to 6750 all weekend long.

http://i.kinja-img.com/gawker-media/image/upload/s--jQv3VBSV--/196fuarapyylmgif.gif

[TooBlue]

What type of PCM/tuning is used on this engine?

[Dan Cragin]

We used an Infinity EMS to tune it on the engine dyno. We would like to use the HP tuners software for the final tune, or we will stick with the Infinity as it interfaces with our Motorsports dash. Maybe Keith might want to share his experience.

[ACR]

We used an Infinity EMS to tune it on the engine dyno. We would like to use the HP tuners software for the final tune, or we will stick with the Infinity as it interfaces with our Motorsports dash. Maybe Keith might want to share his experience.

awesome. please keep this thread up to date with developments and offerings as this becomes available. A Viper at 8k RPM would be sick!

[1ststrike]

That sounds like an unreal motor. Can't wait to see it out there. The V10 block does seem very robust.

[TCurtner]

I would guess a very angry UPS truck...perhaps one that was running late around Christmas time.

This made me lol.
Those things already scare me somewhat when i hear them...imagine 4k more rpm (than they are probably turning). Godzilla.

[345s-bspinnin]

The G4-5 engines do not suffer from the oiling issues like the earlier engines, so they like rpm. The crankshaft driven front pump has its limitations but 7000rpm should be fine.

This is definitely one very sweet build. Can you explain why the 8.4L is not susceptible to the 8.3L oil starvation issues? Is it simply a better OEM high flow/volume oil pump (dry sump in this case), or have the oem oil galleys on the Gen 4/5 crank been modified to more of a chevy style oiling where rod bearings get higher pressure than main bearings (non cross drilled)????

[dewilmoth]

Hoping to resurrect this thread and ask Dan a couple questions regarding the motor mentioned.

How did the reliability end up with this motor, or others like it that you built?Based on what I’m reading, you were comfortable running the motor to 8200 RPM with a stock 100.6mm stroke? No concerns with the high piston speeds? Would de-stroking and longer rods be beneficial enough to warrant the cost, or are you happy with the stock engine geometry?

Also, did you ever solve the VVT issues to make more power at the upper RPM range with a Gen V setup? I have a Gen V and find this engine build intriguing. I appreciate any insight you can provide.

[Aevus]

Hoping to resurrect this thread and ask Dan a couple questions regarding the motor mentioned.

How did the reliability end up with this motor, or others like it that you built?Based on what I’m reading, you were comfortable running the motor to 8200 RPM with a stock 100.6mm stroke? No concerns with the high piston speeds? Would de-stroking and longer rods be beneficial enough to warrant the cost, or are you happy with the stock engine geometry?

Also, did you ever solve the VVT issues to make more power at the upper RPM range with a Gen V setup? I have a Gen V and find this engine build intriguing. I appreciate any insight you can provide.

2nd resurrection for a great thread :-)

I believe Dan mentionned 7,200rpm was the actual rev-limit he was using on the track (with the cam he had).

As far as I understand, the lack of dry sump on the Viper is the real limiting factor for high rev. Neither a swing-arm oil pan or accusump will fix the problem above 7k rpm...

So basically, even with lightweight forged internals, upgraded valvetrain (and with a cam that delivers at high rpm...) Gen3/4 is limited to say 6,300-6800 rpm ?

[GTS Dean]

The solution:
https://www.daileyengineering.com/dodgechrysler/dodge-viper-gen-3-5-wac/

[Steve M]

2nd resurrection for a great thread :-)

I believe Dan mentionned 7,200rpm was the actual rev-limit he was using on the track (with the cam he had).

As far as I understand, the lack of dry sump on the Viper is the real limiting factor for high rev. Neither a swing-arm oil pan or accusump will fix the problem above 7k rpm...

So basically, even with lightweight forged internals, upgraded valvetrain (and with a cam that delivers at high rpm...) Gen3/4 is limited to say 6,300-6800 rpm ?

The rev limiter on my Gen 4 is now set to 6,600. Stock rev limit was 6,400.

[SRT_BluByU]

This is definitely one very sweet build. Can you explain why the 8.4L is not susceptible to the 8.3L oil starvation issues? Is it simply a better OEM high flow/volume oil pump (dry sump in this case), or have the oem oil galleys on the Gen 4/5 crank been modified to more of a chevy style oiling where rod bearings get higher pressure than main bearings (non cross drilled)????

interested in this also..