My 1988 LFX F40 build. (Page 29/67)
Daryl M FEB 27, 09:19 PM
To be fair, comparing modified engines to stock production engines is not a good comparison. If you really want a fair comparison, how about a highly modified LLT vs a highly modified LGX or LFX? That could indicate whether the newer exhaust configuration can make as much power.
Daryl M FEB 27, 09:21 PM
To be fair, comparing modified engines to stock production engines is not a good comparison. If you really want a fair comparison, how about a highly modified LLT vs a highly modified LGX or LFX? That could indicate whether the newer exhaust configuration can make as much power.
Will FEB 28, 09:44 AM
Unless there's a SIGNIFICANT disparity in intake port flow that can't be overcome with port work, I'd put money on a max effort LLT beating a similar LFX. The LGX might be a tougher customer.

And Porsche's 991.2 GT3 RS 4.0 engine makes 520 HP and turns 9000 RPM.
Daryl M MAR 01, 11:14 AM
Will, I would love to see that comparison built.
Joseph Upson MAR 02, 05:26 PM

quote
Originally posted by Will:

Unless there's a SIGNIFICANT disparity in intake port flow that can't be overcome with port work, I'd put money on a max effort LLT beating a similar LFX. The LGX might be a tougher customer.

And Porsche's 991.2 GT3 RS 4.0 engine makes 520 HP and turns 9000 RPM.




To your credit and the increase in knowledge for all of us, I encountered some concern with the new cylinder head design while gathering info on the Camaro5 forum yesterday. Mace is one company that offers a camshaft upgrade for the 3.6L There's a bit of good and bad experience involving them, but an apparent conclusion that some are installing the cams without a tune and expecting magic.

The concern expressed by the individual who purchased the camshafts to install in his modded LLT Camaro, was with the LFX that some already have depending on the year and that some have upgraded to in their LLT platforms. The issue surrounds exhaust scavenging and a possible degree of interference between the exhaust pulses in the consolidated cylinder head, if I understood correctly. They may work well for what they are designed for, while at the same time possibly limiting improvement beyond factory intentions.

The benefit of exhaust scavenging is undeniable, especially when it is maximized with the use of headers, through my own personal experience with it upon learning about what it was after a header install and seeing it in action at the injection air tube check valve attached to the C.A.R.B legal headers.

I mentioned this earlier, but this topic has put a different spin on it for me; GM did an awful lot to the LFX motor to get what amounts to ~11 additional hp in the Camaro, which it has to spin 400 additional rpm to get and the same torque rating although at about 400 rpm lower. Of course that's only a small part of the picture, but still, few of us if any would be happy with those results after having upgraded a motor to larger intake valves, adding .2 additional compression points, higher duration intake camshafts, and the plastic and supposedly better flowing intake plenum all of which the LFX has.

I believe the same mods on the individual port heads would go a lot further than that. When you consider the amount of money GM saved by not having to install two cast iron exhaust manifolds per motor, my thinking is that they sacrificed aftermarket performance potential and made up for it by modifying the indispensable parts for far less than the cost of the manifolds which are actually a nice flowing design.

Here is the link for anyone interested, I've read a few so the info I mentioned may not be in this particular link. Regardless, the motor is an outstanding performer in all its iterations.

The car has headers on it although they're not shown in this link. There's a track meet between him and his wife in the link, not sure what she has in her V6 stang, but he needs to get some of it.

https://www.camaro5.com/for...wthread.php?t=484209

Their race series, love the sound of this motor wide open.

https://www.youtube.com/user/MagnumForceGB

[This message has been edited by Joseph Upson (edited 03-02-2020).]

Will MAR 03, 08:49 AM

quote
Originally posted by Daryl M:

Will, I would love to see that comparison built.




PM me for the address to mail the check.
Will MAR 03, 08:54 AM

quote
Originally posted by Joseph Upson:

The issue surrounds exhaust scavenging and a possible degree of interference between the exhaust pulses in the consolidated cylinder head, if I understood correctly. They may work well for what they are designed for, while at the same time possibly limiting improvement beyond factory intentions.




That's exactly my argument. Everything that headers do for performance is unavailable on the LFX/LGX.

On an even fire V6, the bank firing intervals are 240 degrees. This means that there isn't much interaction from one exhaust event to the next, EXCEPT once the cam duration starts to exceed that number, the next cylinder's blow-down event will compromise the all-important tail end of the prior cylinder's pump-down event. Also, there's no capability to do pulse tuning and very little ability to do momentum tuning, so there it is.
Daryl M MAR 04, 07:52 PM
So I have another question. Do tuned headers improve efficiency? If so why would GM not put them on every vehicle? Aren't Cafe standards are still a big deal for car makers? Anyway, I do remember some 70s Chrysler cars that made more power with stock manifolds than with headers. Would love to see more dyno results about this.
wftb MAR 04, 09:08 PM
The new integrated exhaust manifolds are largely the result of designing an engine from the get go to be more efficient with turbos.Get the turbo as close as possible to the combustion chamber to better make use of the heat and pressure there and then bolt the catylitic converter right to the turbo and you can lower cold start emisions. New turbo v8's from BMW, Mercedes and some others use 2 small turbos where the intake used to be in a conventional V8-in the middle of the V. I am thinking they do not do this with V6's as there might not be enough room in the V.

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

Daryl M MAR 04, 10:55 PM
Doesn't running a turbo defeat the purpose of headers? Besides, most cars are still naturally aspirated.