skank

Since the new Cadillac DPI race car engines are based on the new LT engine, one would think that Corvette Racing's GTLM car would also be developing the LT engine that is in the current production car. The GTLM car is still using the LS engine according to the article below. Any thoughts or inside info when they will change over ??

http://www.enginelabs.com/engine-tec...ew-lt1-coming/

sunsalem

They won't.
The next car CR will be using will most likely be an ME with a DOHC and probably with twin turbos (like the competition).

BTW, this link is from Aug. 2014.

skank

I know it was a old article but it had a lot of good info on the LS engine that they are using. I met Corvette Racings Head Engineer Doug Louth at the 24hrs Of LeMans two years ago and asked him why they hadn't switched over to the LT engine then. He said the LS motor was so highly developed and was so durable that they opted to still use the older block vs the new LT block. You would think they would start developing the LT block since it is in the current Corvettes. There's a good article in www.autoracing1.com about the ECR built LT race engine in the Cadillac DPI

sunsalem

You know the old saying: if it ain't broke, don't fix it.


I've been looking for more info on that motor.
THANX for the link.

JoesC5

The selection of the LS7 block for the C7R(5.5L) is based on the fundamental difference in how the LS7 block is designed and manufactured vs the remainder of the LS blocks and the LT blocks.

That design and manufacturing difference does not apply to the selection of the LT block for the Cadillac racing since it's a 6.2L.

skank

The article on Autoracing1 indicates that the Cadillac DPI is based on the LT4 motor that is shared by Corvette and Caddy. At least they are starting to test the LT4 in racing conditions which has to be good for the ZO6 production cars.

JoesC5

This is what Cadillac said in their press release.

"CADILLAC 6.2L V-8 POWER
The Cadillac DPi-V.R is propelled by a race-prepared, normally aspirated Cadillac 6.2 liter V-8 engine that shares inherent architecture with the engines of the third-generation Cadillac CTS-V (640 horsepower) and fifth-generation Cadillac Escalade (420 horsepower). The engine produces approximately 600 horsepower when tuned for racing as defined by IMSA-mandated air restrictors, with a maximum allowable RPM of 7,600".

It's a normally aspirated engine that is souped up by an aftermarket shop. That's why they also mentioned the Escalade 420 HP engine in their press release, so that people wouldn't think the engine is a detuned supercharged LT4 to get ~600 HP.

skank

I wonder if the block was actually a LT1 Block or a LT4 block. And if there's even a difference.

sunsalem

So, it's a small block Chevy V8.

JoesC5

I don't believe there are any differences between the LT1 and the LT4's block. Internals yes, but not the bare block.

Due to the high RPM capabilities of the race engine, I doubt it uses any internals from either the LT1 or the LT4, especially the LT4's pistons which are low compression(for a N/A engine).

I suspect that the race engine uses an aftermarket crank, rods and pistons, along with a hot cam(and no AFM).

Possible that the race engine does not have DI, but port injection with LS7 based heads. But if they do have DI, I suspect that they would use the same LS7 based heads as used on the 5.5L C7R engine but with slightly smaller valves(because of the smaller bore of the LT block vs the LS7/C7R block).

Frankly, I'm surprised that they would even use the LT block as the re-sleeved LS7 block used on the 5.5L C7R would allow for a slightly larger bore over the LT block, thus a shorter stroke(better for high RPM operation) to maintain the 6.2L displacement.

Bad_AX

That was a good article on the C7R engine over at Engine Labs. I was surprised to see the plastic lifter trays in use in the race engine. The article noted that the lifters were supplied by Jesel. Jesel makes a beautiful dog bone retainer for the LS, and I'm intrigued that Pratt-Miller opted to use the OEM trays.

Does anyone know if the C7R engine uses an 8 counter weight crankshaft (center counter weighted)?

sammy burks

Corvette racing has used DI for about 4 years now.

WzUpDoc

https://arstechnica.com/cars/2017/02...good-race-car/

good follow up article

davepl

Since the blocks are (essentially) the same, and the prime difference between LS and LT motors was the direct injection, and since Corvette racing has been on direct injection for several years, what do you SAY they are running right now?

Sounds like it's neither, but it sounds more like an LT motor than an LS if it's DI, does it not?

Bad_AX

One difference on the LT is the lifter placement that eliminates the offset intake rocker arm. This places the intake pushrod more in the path of the port and possibly restricts the port design compared to the LS square port head.

skank

From the arstechnica article above

That engine is a 5.5L naturally aspirated, direct-injection pushrod V8, a continuing development of the engine from the previous generation race car. With rules capping engine performance at around 500hp, there was little sense in developing a racing version of the current LT4 engine, since it would have to be de-stroked and de-bored down in capacity and couldn't benefit from tricks like variable valve timing. We also asked whether a mid-engined C8.R was on the cards: "Seems like there's always rumors about this," he said laughing.

sunsalem

That is the thing right there...
It only has to have around 500hp, which is something that is easily attainable when working with 5.5L.
Therefore, what the engine really needs to have is dependability, lightweight, and fuel efficiency.
Fortunately, CR has managed find those things with this motor.

JoesC5

Correct, but in a press release I read about the Cadillac engine where it was comparing the race engine to a stock CTS-V LT4 engine, it said the stock engine had "direct fuel injection", but on the race engine it said "fuel injection".

I don't know the significance of why they said "fuel injection" instead of "direct fuel injection".

http://media.cadillac.com/media/us/e...-race-car.html

On interpretation would be that the race engine does not have "direct fuel injection".

Another interpretation would be that there was a misprint in the Cadillac press release

sunsalem

It could easily be that.

skank

This is from the Enginelabs article above. From this comment we can conclude that GM Powertrain Racing has been working on the LT engine for at least 2 years. I wonder why they haven't released it yet.

“Right now we are working on an LT1-based package,” says Russ O’Blenes, manager of GM Powertrain Racing. “We’re in the process, and that’s about as deep as I’ll go into that. We’re trying to figure out what we need to make sure it’s a competitive, reliable package.”