Gen 5 vs Gen 4 engine

[Jack B]

Of all the race engines through here, there is very little evidence that this will actually cause any problems in the long run, it is quite miniscule in percieved effect. If I was to guess, I would say that they probably adjusted the size of the block to head coolant holes. The Gen-3 engines had the same size holes front to back, while the Gen-4 has smaller holes in the front than the back to push flow rearwards. I would bet that they changed the hole sizing to to adjust biasing cylinder to cylinder.

All that said, the Gen-4's had headgasket problems in some cases, that SRT has apparently credited towards the cooling system "hot spots"- but I don't agree. It was a bad gasket design, I saw possible issues the first time I saw them. Cylinders running a few degrees warmer than their sisters dont cause head gasket failures unless there is a head gasket weakness, or a major cooling system failure upstream.

This could be fact or fiction, but, at VOI the SRT engineers said something like this:

"We found the Gen IV engine had an issue with uneven block cooling, leading to some cylinders running hotter than others. We spent a lot of time on the GEN V engine so that it would not have the same problem"

He spent quite a bit of time explaining the pains they went through to achieve the new cooling scheme. I am fairly sure he indicated that since they were pushing the envelope further they wanted to improve the cooling gradient across the block.

There is another issue, I am sure since they went to the composite intake, the heads and therefore the combustion chamber would have seen some temp rise from the reduction in heat sinking. This could have been the main reason they looked at the cooling efficiency.

 

[Viper Specialty]

This could be fact or fiction, but, at VOI the SRT engineers said something like this:

"We found the Gen IV engine had an issue with uneven block cooling, leading to some cylinders running hotter than others. We spent a lot of time on the GEN V engine so that it would not have the same problem"

He spent quite a bit of time explaining the pains they went through to achieve the new cooling scheme. I am fairly sure he indicated that since they were pushing the envelope further they wanted to improve the cooling gradient across the block.

There is another issue, I am sure since they went to the composite intake, the heads and therefore the combustion chamber would have seen some temp rise from the reduction in heat sinking. This could have been the main reason they looked at the cooling efficiency.

Jack-

I think I/we/they are basically talking about the same thing. The most economical method of changing the temp gradient accross the cylinders would be to adjust the flow to a given portion. Given that they adjusted the flow for the Gen-4 compared to previous generations, it makes sense that there may have been a miscalculation. It is not impossible they modeled the Gen-4, and then actual results indicated that it was not perfect, so they installed sensors across the engine to check their work, and adjust as necessary.

However yes, I absolutely agree that this may be more of a hindrance on Gen-5 than 4 due to other design changes. The increased power output, decreased heat sink/transfer capability and cooling from airflow of the plastic manifold, and increased heat transfer of sodium filled valves would all contribute to increased head temperatures and/or increased gradients from cylinder to cylinder.

 

[ipetrov]

It seems to me SRT has gone the LS7 route a little bit to squeeze that last 10% of EPA-approved performance - lighter valvetrain / higher revving / higher hp engine, which jives with Randy Pobst's surprising comment that "it's a high revving engine, not a torque monster". Almost sounds like an LS7 with 2 more cylinders.

Hopefully there will be no "Dropped Valve Club" like in the Z06s, as the sodium filled exhaust valves (along with other variables) in those have definitely been blamed for the problem.

 

[ACRucrazy]

Tell me Pobst's statement wasnt incorrect.
The most torque of any naturally aspirated sports car on the planet.

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[ipetrov]

He says that around the 7.30 mark in the video:

http://www.youtube.com/watch?feature=player_embedded&v=0lK_b-5gerM

Don't get me wrong, I hope he's totally wrong. It's maybe just a perception caused by the combination of VVT (waking up in high 3000's) and lighter rotating assembly. Plus, compared to the Gen IV in the graph above, the difference becomes a lot more pronounced (and increasingly so) after 4.5k RPM.

 

[ACRucrazy]

I know he says it, i laughed when I heard it because of how incorrect it was by saying its not a torque monster.

 

[Torquemonster]

They had a slight problem with certain cylinders running hotter than the average. You can change the a/f and timing based upon the temps of the upper cylinder chamber. The factory has always dumped loads of fuel (over rich) at wot to cool the charge, that costs hp.

Just tune each cylinder individually ;-)

... but you will need a lot of extra sensors lol

 

[SRT09]

Can Dan or anyone confirm if Gen 5 pistons and rods will work in a Gen4?

 

[Viper Specialty]

Yes they will, but will require crank balancing.

 

[Fire196]

All the Gen 5 internals will fit in a gen 3 block I know because I've done it with the help of prefix The only exception was I had to shorten the crank by half an inch to accommodate the front cover being slightly shallower than the Gen 4 or 5. The block had to be bored 25 thousand over and I used Gen 4 heads and a drag pack intake so it's still drive by cable. Prefix reflashed the computer and the car drives unbelievable.

 

[99RT10GTS]

All the Gen 5 internals will fit in a gen 3 block I know because I've done it with the help of prefix The only exception was I had to shorten the crank by half an inch to accommodate the front cover being slightly shallower than the Gen 4 or 5. The block had to be bored 25 thousand over and I used Gen 4 heads and a drag pack intake so it's still drive by cable. Prefix reflashed the computer and the car drives unbelievable.

I bet that car runs like a rapped ape. What did it dyno at?