Dodge Challenger Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
209 Posts
Discussion Starter #1
I’ve been wondering why the Hellcat is rumoured to be a supercharged 6.2 Liter engine, and not a supercharged 6.4 Liter. Are there some design considerations that would warrant machining a separate block, heads, pistons, etc.? From strictly a manufacturing point of view, it would seem cheaper to slap a supercharger on the 392 and go from there. Maybe this question has been asked before, and it could all be speculation anyway. I am interested in knowing if there are benefits to the 6.2 L from an engineering standpoint.
 

·
Registered
Joined
·
4,293 Posts
...um whatever that means, but the 6.2 was developed to boost, the 392 was not. We are only talking about .2 liters, there is no significant loss with the slight downsizing I'm sure.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #5
Speaking of displacement, I suppose they could have changed the stroke and left the bore the same. Would be interesting to know the bore and stroke.


Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
7,683 Posts
Maybe it essentially is the 6.4 L Hemi...just that, when you introduce forced-induction, it usually helps to back off compression ratio a bit. So a simple way to do that is to reduce the stroke? When you reduce the stroke, maybe you lose a bit of displacement? You'll still come out way ahead in output, being able to leverage more boost with a more boost-tolerant compression ratio.

The caveat...now it becomes a direct pissing match over hp rating with the ZL-1, maybe?
 

·
Registered
Joined
·
36 Posts
I believe you are correct. When Cadillac supercharged the NorthStar V8, they reduced the displacement (bore) by .2 liters to make the block stronger for supercharging, and more "meat" for the head bolts and gaskets to attach to. These changes were made to help the engine deal with the boost pressure.
 

·
Premium Member
Joined
·
6,492 Posts
Are there some design considerations that would warrant machining a separate block, heads, pistons, etc.? From strictly a manufacturing point of view, it would seem cheaper to slap a supercharger on the 392 and go from there. Maybe this question has been asked before, and it could all be speculation anyway. I am interested in knowing if there are benefits to the 6.2 L from an engineering standpoint.
What makes you think a 6.2L would be a completely different engine? The 6.4L is a modified 5.7L, it's not a completely different block, etc so there's no reason to think that a 6.2L would be completely different.

It will be interesting to see what the actual specs are, once we see what bore x stroke and CR are then that should be pretty revealing.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #9
What makes you think a 6.2L would be a completely different engine? The 6.4L is a modified 5.7L, it's not a completely different block, etc so there's no reason to think that a 6.2L would be completely different.
I don't think it's completely different. I am more curious about if the difference is in the bore or stroke and why.



Sent from AutoGuide.com Free App
 

·
Premium Member
Joined
·
1,582 Posts
Bore and stroke will really be the only difference. I'm sure everything will be forged to go along with the blower.
 

·
Super Moderator
Joined
·
15,023 Posts
Maybe left the bore a little thicker to deal with the boost hence a little less displacement, 6.2 vs 6.4 (just a guess).

Sent from AutoGuide.com Free App
Similar thing when Chevy was building up the ZR-1 engine - smaller bore for thicker cylinder walls...better durability with the boosted engine.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #12 (Edited)
If the same bore as the 6.4 were maintained (4.09) then a 3.60 stroke would get you to 6.2 L (378 ci). Conversely if the 6.4 stroke (3.80) is maintained, this results in a 3.98 bore. Of course it could be a combination of change to both. I would enjoy hearing about the design from an srt engineer. Would be cool to hear from Chrysler.

Both arguments are good...reduced compression for supercharging (shorter stroke), or reduced bore for strength. I would guess that it's a reduced stroke, but that's an engineer's shot from the hip. Thinking that the laws of thermodynamics are more critical than the integrity of the block.


Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
1,398 Posts
What makes you think a 6.2L would be a completely different engine? The 6.4L is a modified 5.7L, it's not a completely different block, etc so there's no reason to think that a 6.2L would be completely different.

It will be interesting to see what the actual specs are, once we see what bore x stroke and CR are then that should be pretty revealing.
When you say it like that, it gives the impression (to me at least) that they just took a 5.7 block then bore/stroked it.

They used the same design but the 6.4 starts as a 6.4 block.
 

·
Premium Member
Joined
·
6,492 Posts
When you say it like that, it gives the impression (to me at least) that they just took a 5.7 block then bore/stroked it.

They used the same design but the 6.4 starts as a 6.4 block.
Point is, it's not a completely different engine. Whether they cast it as a 6.4L block or a 5.7L and bore it out, it's still based on the 5.7L and there are tons of shared parts. You're making the 6.4L sound like it's similar to the 6.1L which wasn't based on anything. :) The amount of engineering/effort required to build a 6.2L is minimal, they're not going to reinvent the wheel. That's all I'm sayin'.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #15
As I understand it the 6.1 was based on the previous generation 5.7, while the 6.4 is based on the newer generation (gen III?) 5.7. Still, the 6.4 has reinforced bulkheads (if memory serves) which leads me to believe that it's an entirely separate cast, although design-wise based on the new generation 5.7. Hope I'm correct on this...


Sent from AutoGuide.com Free App
 

·
Premium Member
Joined
·
6,492 Posts
As I understand it the 6.1 was based on the previous generation 5.7, while the 6.4 is based on the newer generation (gen III?) 5.7. Still, the 6.4 has reinforced bulkheads (if memory serves) which leads me to believe that it's an entirely separate cast, although design-wise based on the new generation 5.7. Hope I'm correct on this...


Sent from AutoGuide.com Free App
I think you're getting confused, the 6.1L has the reinforced bulkheads. The 6.4L/392 crate engine is based on the 6.1L but was never used in production vehicles while the production 6.4L/392 is based on the Gen3 5.7L.

I haven't done the math, but apparently if the crank from a 5.7L is used in a 6.4L then that would provide 6.2L (rounded to the nearest tenth) so they may just drop a forged 5.7L crank in there with some upgraded pistons and connecting rods. That would be the simplest (and cheapest, IMO) way to achieve that displacement.

I'm not saying the 6.1 isn't or couldn't be based on the earlier 5.7, but I haven't seen anything indicating that's the case.
 

·
Registered
Joined
·
209 Posts
Discussion Starter #17 (Edited)
I haven't done the math, but apparently if the crank from a 5.7L is used in a 6.4L then that would provide 6.2L (rounded to the nearest tenth) so they may just drop a forged 5.7L crank in there with some upgraded pistons and connecting rods. That would be the simplest (and cheapest, IMO) way to achieve that displacement.

You're right. 4.09 x 3.58 stroke yields 6.17 L. Whatever the case, I hope details on CR, bore, stroke and boost will be available. It will interesting to see what the Chrysler engineers come up with versus aftermarket SC on a 392. I've seen a couple of posts recently where the stock motors (5.7 and 6.4) threw a rod.



Sent from AutoGuide.com Free App
 

·
Registered
Joined
·
710 Posts
I’ve been wondering why the Hellcat is rumoured to be a supercharged 6.2 Liter engine, and not a supercharged 6.4 Liter. Are there some design considerations that would warrant machining a separate block, heads, pistons, etc.? From strictly a manufacturing point of view, it would seem cheaper to slap a supercharger on the 392 and go from there. Maybe this question has been asked before, and it could all be speculation anyway. I am interested in knowing if there are benefits to the 6.2 L from an engineering standpoint.
After today's preview at the NY auto show, I don't think you're even going to see a 6.2 supercharged hell cat with a dodge name on it, hasn't anyone noticed there are no Challenger SRT's being talked about, they are calling them Scat pack cars and 392 R/T's. As of January you could not order a SRT from Dodge and then in late Feb you no longer could order a Core SRT which seems to be the new 392 R/T. The question is, is the SRT Challenger gone only to return as a SRT brand Hellcat or something with some stupid price tag like the viper which by the way has been taking up space at my local dealer ever since they introduced it and if I was stupid enough I could probably by below cost and they would love me for at least a while.
 

·
Registered
Joined
·
4,964 Posts


“fargo59” wrote that it shares heads with the Apache SRT 6.4 Hemi engine. which may also indicate a large bore, short stroke design (6.4 is 4.090” bore, 6.1 was 4.055”). A 4.090” bore with a 3.58” stroke would be 376 cubic inches, or 6.16 liters. “A 6.4 with a forged 5.7 crankshaft would give the right dimensions and be relatively easy to work; a shorter stroke is also going to give the idea rod to stroke ratio and make it a high revving engine.” Cams are also reportedly similar to the 6.4 design; the block is said to be identical.

Supercharged 6.2 Hemi: ?HellCat V8?
 
1 - 20 of 23 Posts
Top