240hp uh?

[BNaylor]

Originally Posted by TDWPgtp

i want that kinda power and mpg!

Then buy the Hyundai Genesis Coupe or a car that wasn't first introduced back in 1996.

[robkiehl21]

Originally Posted by TDWPgtp

dont get me wrong, i love grand prixs, but is it just me or do our engines seem extremely inefficient. looking at some newER cars with similar size engines, ive noticed way more hp and way better economy. take the Genesis Coupe. it has a N/A 3.8 making 306 hp. thats 66 more hp from the same size engine with no S/C. ANDDD it gets better economy. thats just one example but i think you get my point. its just dissapointing to see how much more efficient other cars are. i want that kinda power and mpg!

You're forgetting that the 3800 V6 engine is basically a 40 year old design, it started out in the 60's (or 70's cant remember exactly) in buicks... It is an iron block pushrod 12 valve engine. The 3.8 in the genesis, or the 3.8 in the mitsubishi eclipse gt are aluminium and have 24 valves, as well as much more freely flowing intake and exhaust ports. Most newer engines also have variable valve timing, direct injection, and higher compression ratios. Personally, I am no fan of pushrod engines, but I love the 3.8 s/c in my grand prix.. Huge amounts of torque, and I get 24 mpg average, which for about 270 horsepower in mine, is pretty good in my opinion. You can't expect a 40 year old engine to compete with modern technology, but the 3800 has done pretty well, as it was one of the last pushrod OHV engines to still be put in cars (not counting the LS series v8s), only being discontinued a couple years ago.

[TDWPgtp]

learn somethin new every day i guess ha thanks

[CrazyHorst]

Good info above. Just to add a couple of things...the iron-head hurts the peak hp performance of any engine because the engine is going to be knock limited (can't use full MBT spark advance as you'd destroy the engine). The pushrod valvetrain and relatively large 2-valve components limit the redline....although my personal belief is that the 3800 is the highest evolution of a pushrod valvetrain used in an iron-head engine (other that possibly some corvette derivatives...but I consider those anodized CNC rocker arms to be inferior for durability reasons over the nice investment-cast ones used in L36 and L67)

Back to the classic equation, HP = torque * rpm / 5252 (using SAE units). So imagine the horsepower you could make if you could spin the engine up to 14000 rpms...you get the picture that there isn't any free lunch.

What a 3800 has is lots of torque as mentioned. The supercharger only helps. Personally I think you get very excellent fuel economy with a 3800 of any variety.

A couple of other thoughts relative to practical considerations...the 3800's emission performance is *excellent* compared to almost everything else out there. The short-iron-exhaust-port keeps a very large amount of heat in the exhaust stream which helps catalysts out. Also consider that the 3800 was made at a peak volume of nearly 5000 engines per day out of a single manufacturing plant, all with net-build (unlike some manufacturers who batch-sort parts based on dimension..nice to do but forget about volume)...I don't think you'll ever see that again from anyone else.

Another mistake is to think that each aftermarket mod is additive to total hp. That was one dyno run my friend...and nobody will ever know whose lunchbox was on the torque-reaction-arm while the dyno was calibrated or what kind of perfect moist-air sea-level standard-air device was used to feed the engine.

But what we're getting at here is the reasons behind the end of the 3800....relatively large mass...and the engine is never going to be 300hp advertised without aluminum heads, etc....or 50 degree water-to-air intercoolers....or 102 octane gas...the numbers on those get close. The public doesn't care, they want to compare vehicles on peak HP numbers and not what the cage can do.

[CrazyHorst]

Also...just recalled...the L67 was somewhat in response to Ford's 3.8 Tbird SC which came out earlier and later on the SHO. The 3.8SC was a catastrophe in packaging with pipes, hoses and tubes running all over the place. The boys from Flint popped it on top of the balance shaft and said how ya like me now? A supercharged engine don't need a fancy intake manifold.

Huge cost savings in production volumes nonetheless.

[CrazyHorst]

Just to underscore one more point...a 4-valve head has a huge advantage in "volumetric efficiency" due to the valve area....or in other words it "flows" a lot better at higher RPMs. In a 2-valve head, the mixture-motion or "combustion chamber swirl" which induces excellent low-end torque becomes a restriction as flows increase.

The downside of the 4-valve head is that with all that valve area there's equivalently more "spitback" of essentially EGR when the intake valve opens with a partial vacuum on one side and low-positive, but near-atmospheric exhaust pressure from the last combustion event. Essentially the 4-valve has considerably more "EGR" at low rpms which is directionally wrong for producing torque.

The other issue is most 4-valves I've been near with appropriate instrumentation went quickly to piston protection (overfueling) partially due to the valve reliefs and sharp edges on the piston face. Waste of fuel integrated over a long time.

This isn't to say one is better than the other, IC engine design is about tradeoffs and balances, there is no free lunch so to speak. Just developing a engine-hardware and control package with a nearly flat and not super-peaky torque curve is a huge challenge in itself. Then comes durability, sealability, emissions, fasteners, manufacturing all the components to dimension, assembling the product...lots and lots of engineering development behind any powertrain after you get past the IC theory "pathway" which has been chosen.

[Fastlane89]

^^^ Better technology = better effeciency. The GTP GP was probably top of the class when it was first unveiled in terms of torque and HP...some V6's still dont stack the same kind of HP and torque, though 300+ HP 6 cylinders seem to be setting a standard these days.

Oh and by the way, unless your planning on racing the Nurburgring, i wouldnt focus so much on horsepower as i would on torque. Increasing the torque will not only leave those pathetic jap-craps in the dust, it will make them never want to screw around with another American again.

[BNaylor]

Originally Posted by Fastlane89

Oh and by the way, unless your planning on racing the Nurburgring, i wouldnt focus so much on horsepower as i would on torque. Increasing the torque will not only leave those pathetic jap-craps in the dust, it will make them never want to screw around with another American again.

Thats why I like watching the Fast & Furious movies in Blu-Ray of course.

But I have my own experiences blowing the doors off of 350Zs and G35s just to name a few with my GXP.

[l67cooled]

I'm surprised no one mentioned how all dyno's are a bit different; especially when comparing a dyno jet to a mustang dyno. Some dyno comparisons have varied up to 10% difference. You really can't compare to other dyno's you've read. Although you can see your difference if you continue to mod and use the same dyno.

If I remember right the stock 4t65-hd will roughly loose 15 to 17% hp from the crank to the wheels.

OP if you pulled 240 whp with the little bit of mod's you've added then I'd say you did pretty well. You have to realize not all your mods are adding much HP if any at all.