IMSA DPi Discussion

[hondafan37]

Originally Posted by DistortedSmile

The Mazda is a work of art, shame it doesn't have a 4-rotor in the back to make it sound as good as it looks

Originally Posted by wdave0
Jim Downing's Kudzu 4 rotor sounded great without being annoying and ran very well - I believe that was the last 4 rotor racing. Agreed, the 787 was a bit too loud

Originally Posted by CyberMotor
I agree, the four-rotor was one sweet sounding machine. It was very close to sounding like the V-12s.

If the RX-9 is manufactured, perhaps the DPI 2019 will have this new rotary engine.
http://www.caranddriver.com/features...ng-for-feature

[seanyb505]

Mazda said it officially is dead last week or something.

[knighty]

Does anyone know anything about the Cadillac DPi engine? this looks like a 2-valve per cylinder motor based on the rocker-covers in the pictures, I'm guessing with GM origins, is this perhaps just the previous DP GM engine installed into a DPi or is it a different animal all together?.....perhaps Corvette based?......I seem to remember its 6 litres or something?......should have a huge torque and drivability advantage over all the other engines due to its large capacity, by quite some margin.

[Matt]

6.2l based on the new LT architecture.

Old DP engine was 5.5l, LS based.

[knighty]

Interesting, so the new LT is GM based for the Corvette, so from the links below it looks like a small-block direct injection upgrade of the old LS engine, also with variable valve timing to allow high rpm performance, but if they have any sense they will have removed that junk from the race engine, as in my experience its too slow to react to add any real performance benefit on a race motor.

http://www.chevrolet.com/performance/crate-engines/lt1.html

http://www.superchevy.com/news/ghtp-1210-gen5-inside-gms-all-new-lt1-small-block/

[Matt]

VVT is generally banned in all forms of motorsport anyway.

[JHamilton]

Originally Posted by knighty

Interesting, so the new LT is GM based for the Corvette, so from the links below it looks like a small-block direct injection upgrade of the old LS engine, also with variable valve timing to allow high rpm performance, but if they have any sense they will have removed that junk from the race engine, as in my experience its too slow to react to add any real performance benefit on a race motor.

http://www.chevrolet.com/performance...gines/lt1.html

http://www.superchevy.com/news/ghtp-...1-small-block/

The LT is the gen V SBC and actually shares no parts with the venerable gen IV LS. The block design is a development of the LS, however. As you would expect with DI, the head design is completely different and compression is raised.

VVT was a point of contention among SBC nerds but seems to be settling down. Some companies are producing single-bolt VVT cams some are offering delete kits with an LS cam cover and a three-bolt cam. It seems for street/track use most are using a VVT cam to keep the benefit at low revs. The drag guys are deleting. Both setups can produce well over 1000hp on pump gas.

The 5.5L in the DPs was a LS-based but direct injected. It was the proof of concept for the gen-5.

[canaglia]

Originally Posted by Matt

6.2l based on the new LT architecture.

Old DP engine was 5.5l, LS based.

yeah, old 5.5L was basically an enlarged version of the 5L used before 2014 by corvette DP, that was no more than a race tuned LS3.
Guess that engine was folded because wasn't efficient and reliableanymore if pushed up to 600hp.
New engine is a race tuned LT1 revving up to 7600rpm (corvette c7 peak power of about 450hp is achieved at 6000rpm or less).

C7R motor should still be using LS7R architecture, destroked to 5.5 + DI

[Matt]

Originally Posted by canaglia

yeah, old 5.5L was basically an enlarged version of the 5L used before 2014 by corvette DP, that was no more than a race tuned LS3.
Guess that engine was folded because wasn't efficient and reliableanymore if pushed up to 600hp.
New engine is a race tuned LT1 revving up to 7600rpm (corvette c7 peak power of about 450hp is achieved at 6000rpm or less).

C7R motor should still be using LS7R architecture, destroked to 5.5 + DI

You're joking, right?

The engine was retired simply because they wanted to promote the LT instead.

[canaglia]

Originally Posted by Matt

You're joking, right?

The engine was retired simply because they wanted to promote the LT instead.

consider that to achieve about 550hp that engine revved up to 7500rpm, to hit 600hp had to consume more fuel and rev close if not over 8000rpm.
Surely reliability and consumes are not improved...
It's just a speculation of mine, but with a much more serious approach

[Maelochs]

I think the reason for the engine switch had more to do with the fact that the LT block is also the basis of the engine in the consumer Cadillac. Back when GM was trying to push "Corvette DP" it used a Corvette engine as a base. Now GM is promoting its "Cadillac DPi V.R." which has a Cadillac based engine. Sort of makes sense.

I am pretty sure Chevy could get 600 reliable horsepower from the LS block ... Pretty sure it has been used in competition cars of all types for years and makes a lot more than that in some applications.

Just to be fair, I have to admit this is all conjecture.

[canaglia]

Originally Posted by Maelochs

I think the reason for the engine switch had more to do with the fact that the LT block is also the basis of the engine in the consumer Cadillac. Back when GM was trying to push "Corvette DP" it used a Corvette engine as a base. Now GM is promoting its "Cadillac DPi V.R." which has a Cadillac based engine. Sort of makes sense.

I am pretty sure Chevy could get 600 reliable horsepower from the LS block ... Pretty sure it has been used in competition cars of all types for years and makes a lot more than that in some applications.

Just to be fair, I have to admit this is all conjecture.

Didn't say it was impossible to get 600hp from that engine, just that would it turn unreliable and less efficient.

Look at street C6 ZR1 or C7 Z06. GM prefered to use supercharged versions of their LS3/LT1 motors instead of use NA LS3/LT1 engines revving up too high

[Matt]

An all-motor LS will be stupid reliable at 600hp.

[Maelochs]

Originally Posted by canaglia

Didn't say it was impossible to get 600hp from that engine, just that would it turn unreliable and less efficient.

Originally Posted by Matt

An all-motor LS will be stupid reliable at 600hp.

Given that I cannot remember Ever seeing a blown GM motor at a Rolex race (I did see Scott Pruett's Ganassi Riley-BMW puke out its transmission an hour or so short of winning the Rolex) I am pretty sure that reliability was never an issue. I am not going to do the research, but I seem to recall a lot of desert racers using GM motors ... and there is no tougher environment.

I don't know about fuel consumption---the new motor is bigger, and I don't see how it could run a lot leaner ... but again, this is all conjecture.

One thing I am thinking is that with the bigger motor, possibly there is more room for even more growth in power in the years to come.

Can you imagine one of the new DPis with 700 bhp?

[JHamilton]

Originally Posted by Maelochs

I think the reason for the engine switch had more to do with the fact that the LT block is also the basis of the engine in the consumer Cadillac. Back when GM was trying to push "Corvette DP" it used a Corvette engine as a base. Now GM is promoting its "Cadillac DPi V.R." which has a Cadillac based engine. Sort of makes sense.

I am pretty sure Chevy could get 600 reliable horsepower from the LS block ... Pretty sure it has been used in competition cars of all types for years and makes a lot more than that in some applications.

Just to be fair, I have to admit this is all conjecture.

Yes, and it's the just new GM small block (why do we continue to say "small block"? Wishful thinking that a big block is on the drawing board? ). They sharpen the knives just like every manufacturer.

Originally Posted by canaglia

Didn't say it was impossible to get 600hp from that engine, just that would it turn unreliable and less efficient.

Look at street C6 ZR1 or C7 Z06. GM prefered to use supercharged versions of their LS3/LT1 motors instead of use NA LS3/LT1 engines revving up too high

Regarding the race engines, there is very little difference in reliability or efficiency since the LS was switched to DI a few years ago.

We could build an LS with over 600 hp in your garage and it would last forever. There are tons of companies that will sell you one with a warranty. The reason superchargers are used on the street engines is driveability. We could put that LS we built in your garage into any car and it would go forever. You wouldn't want to drive that car to work, however, as it is quite the production and difficult to manage under 10 mph. With a supercharger, you get the power without the nasty cam. Off boost and at low revs, it's a sweetheart just like a stock LS/LT.

[JHamilton]

Originally Posted by Maelochs

I don't know about fuel consumption---the new motor is bigger, and I don't see how it could run a lot leaner ... but again, this is all conjecture.

One thing I am thinking is that with the bigger motor, possibly there is more room for even more growth in power in the years to come.

Can you imagine one of the new DPis with 700 bhp?

Keep in mind that the last of the gen IV (LS3, LS9, LSA) were all 6.2L as well. The bore and stroke of the race engines was reduced to meet displacement regulations. Fuel consumption vs displacement is pretty linear in a pushrod engine. Meaning, at the same power output the larger engine is at lower revs and using less fuel. I'm sure there are differences but I think it is a wash for the most part.

[MoMedic9019]

Lol. That LS motor will make 750+ without batting an eye.

[Starfish Primer]

Is still RCR building those engines or have they moved to Pratt Miller?

[Maelochs]

Originally Posted by Starfish Primer

Is still RCR building those engines or have they moved to Pratt Miller?

I believe I saw an RCR decal on the Caddy valve cover ... let me look through some photos .... Nope, ECR .... oh, well.

Funny, because i thought, mistakenly, that it was Childress Racing ... who knows what gaps there are in my mental function that I overlook until others point them out.

[Matt]

Originally Posted by Maelochs

I believe I saw an RCR decal on the Caddy valve cover ... let me look through some photos .... Nope, ECR .... oh, well.

Funny, because i thought, mistakenly, that it was Childress Racing ... who knows what gaps there are in my mental function that I overlook until others point them out.

ECR = RCR.

[Maelochs]

Originally Posted by Matt

ECR = RCR.

Dang, I at least thought I knew the alphabet. Wow, this is depressing.







Doh .... Earnhardt/Childress Racing, not Richard Childress Racing. I am pretty far out of touch.

[carbsmith]

Originally Posted by Starfish Primer

Is still RCR building those engines or have they moved to Pratt Miller?

Earnhardt Childress Racing Engines has and continues to build the DP engines. At this point ECR Engines is more or less just RCR's engine shop as the only other half-competitive car they provide engines for is the #13 but it is still partly owned by Dale Earnhardt Inc.

The GT1 and GT2 Corvette engines were built by Katech, but the GTE engines are now handled in house by GM Powertrain alongside the ATS-V.R engine and the factory programs for IndyCar, NASCAR, and drag racing.

[Bcarr6]

Hmmmmmm

[Matt]

Nissan:

[hondafan37]

ESM Ligier Nissan DPi Revealed; Testing Begins

http://sportscar365.com/imsa/iwsc/es...esting-begins/