Flat Plane Crank LT5

[mgbrv8]

Freshly rebuild LT5 thanks to a grenaded oil pump. They replaced the stock crank with a flat plane. It still isn't broken in yet. I hope the video and the pics work


Video:
https://www.facebook.com/holger.hove...3/?pnref=story


Pictures
https://www.facebook.com/norbert.vor...7474204&type=3



David Hetrick

[Fully Vetted]

Would this not be the largest displacement engine ever made with a FPC? I know Fords Coyote is the largest displacement FPC for a OEM at 5.2L. Not sure about aftermarket and/or racing applications.

[mgbrv8]

Originally Posted by Fully Vetted

Would this not be the largest displacement engine ever made with a FPC? I know Fords Coyote is the largest displacement FPC for a OEM at 5.2L. Not sure about aftermarket and/or racing applications.

Boy that is a good question. Im going to ask around?


Dave

[LGAFF]

I believe the Lotus GT-1 was 6.0 Liter

Renewing their ties with General Motors, they managed to get hold of a set of 5.7L LT5 V8’s. Lotus had helped develop this engine for the Corvette ZR1 when it was still a GM subsidiary. The engine was fitted with a flat-plane crankshaft and its displacement was increased to 6.0L. It eventually developed 615 horsepower with FIA-mandated 36mm intake restrictors.

[Hog]

"The factory GT1 Lotus Racing team (run by Fabien Giroixs-First Racing )would be the only ones to opt for the Chevrolet V8 instead of the Lotus 3.5 V8 turbo unit." The other privateer teams (GBF UK and Martin Veyhle Racing) stayed with the 3.5 turbo V8. These 3 teams got the 7 chassis that were built.

The flat plane LT5 was eventually replaced by Dodge V-10's in the Elise. Talk about a step----down. The V-10 couldn't match the lackluster performance of the Chevrolet LT5 V8 or the even worse Lotus 3.5 turbo engine. While the Lotus developed LT5 was a good engine, it was competing against race bred engines and apparently did have the top end power that other pure race engines were delivering.

Here are some LT5 pics the Lotus Elise GT1.(at least I think they are LT5 derivatives. Its tough to decipher as the 3.5 Lotus was a V8 as well, though it was turbocharged

[A26B]

The Moldex flat plane crank was coordinated through Jerrys Gaskets, as well as some gaskets & seals. The Main Studs were developed by Todd Pepmeier.

We are glad to have played a small part in the project.

[Jagdpanzer]

Originally Posted by A26B

The Moldex flat plane crank was coordinated through Jerrys Gaskets

Jerry,
Another excellent example of support for the LT5 ZR-1 brotherhood!!
How was Moldex to work with and what was their lead time to design and produce the crank?

[tpepmeie]

Hog's pics are indeed the 3.5L twin-turbo V8, not the LT5. You can see the lotus casting logo on the cylinder head, and the turbo plumbing (hard to see).

[XfireZ51]

Would someone clarify what a Flat Plane Crank is, what are the benefits?

[tpepmeie]

Dom,
Imagine the crank throws all on the same "plane", rather than at 90 degrees to each other. Usually it is "up, down, down, up" for the 4 rod journals. Still have a cylinder event every 90 degrees, but they alternate banks (Left, Right, Left, Right, ...). And all the firing intervals are evenly spaced on each bank. Helps exhaust tuning quite a bit, and all cylinders exhibit the same airflow performance. On a 90 degree V-8, certain cylinders can perform up to 8-10% worse than the best cylinder due to exhaust tuning (mainly the closely spaced (90 degrees apart in the firing sequence) cylinders on each side.).

The downside... a considerable secondary shake, in the side-to-side axis. Not as naturally well balanced as a 90-degree crank. And-you can't run a large stroke due to this vibration.