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tpepmeie · 09-09-2014

The engine in the video is a different engine, but similar intake.

The Lotus GT-1 engine was 4.00 bore x 3.64" stroke, flatplane crankshaft. I have the blueprints for that crank, as a matter of fact. Just under the 6L limit of the GT-1 rules of the time (1997).

It ran stock size valves, at least initially. Comp ratio was "more than 12.0:1"

The engine ran in competition through a pair of 34.3mm intake air restrictors, such was the rules at LeMans back then. At Silverstone, running that restrictor size, the engine made peak power at 7300 rpm, 570bhp. Over 600bhp was available if the car ran at the larger restrictor size afforded for 1000kg weight.

LeMans engines were built for endurance, and so peak power speed was in the region of 6600-6800 rpm.

Graham once included an unrestricted Dyno sheet in a presentation at BG. According to that the engine made 620bhp @ 7000 rpm, and ~480 lb-ft @ 5000. LPE assisted Lotus on the project.

I wasn't a part of any of this, but most of the above was written in a Race Tech article from the era.

Todd

09-09-2014	#9
tpepmeie Join Date: Aug 2005 Location: Fishers, IN Posts: 812	Re: LT5 race engine The engine in the video is a different engine, but similar intake. The Lotus GT-1 engine was 4.00 bore x 3.64" stroke, flatplane crankshaft. I have the blueprints for that crank, as a matter of fact. Just under the 6L limit of the GT-1 rules of the time (1997). It ran stock size valves, at least initially. Comp ratio was "more than 12.0:1" The engine ran in competition through a pair of 34.3mm intake air restrictors, such was the rules at LeMans back then. At Silverstone, running that restrictor size, the engine made peak power at 7300 rpm, 570bhp. Over 600bhp was available if the car ran at the larger restrictor size afforded for 1000kg weight. LeMans engines were built for endurance, and so peak power speed was in the region of 6600-6800 rpm. Graham once included an unrestricted Dyno sheet in a presentation at BG. According to that the engine made 620bhp @ 7000 rpm, and ~480 lb-ft @ 5000. LPE assisted Lotus on the project. I wasn't a part of any of this, but most of the above was written in a Race Tech article from the era. Todd