why didnt LIRR go with Comet MU's instead of Double Deckers

The Genesis is not slow by any means, a single genesis with 7 bombardiers accelerates to 60 mph at same speed as a FL9 train and 7 bombardiers.
It could have been way faster if they had geared it for 85 mph instead of the ludicrous 110 mph, that is a 25% loss in acceleration right there.

Those things are geared for 110!!! Damn!

I'm sure that if they actually had put a decent amount of effort into the design process, they could've come up with a C3 type MU. But that's not what the thread is about. Those would be instead of the M7s. We're talking about what else could've been used for the DIESEL cars.

Honestly, I think the C3s were a good choice. There was a capacity requirement set. They made it. They went bi-level b/c they went with 2x2 seating, and passengers are greatful for the 2x2 seating. They also went with double deckers b/c if they had not, the platforms would've had to have been raised to a much longer length than what they were, which I'm fairly confident would've resulted in more station closures, such as Glen St and probably more on the Montauk.

<i>They went bi-level b/c they went with 2x2 seating</i>

No, the C1s were 3X2 on both levels. The decision to go bilevel was made BEFORE the one to go 2x2. IMHO, it was because Prendegast was from Illinois and figured if it's good for Metra it's good for everyone....

That would be a myth Phil as they do not have double deckers in Illinois.
They have Gallery cars a complete different beast with 2x2 on lower level and single seats at upper level.
The C1's were an experimental car, based on components of the M1/M3.
All electricals and interior filttings were identical, Door mechanismes were identical Vapor/Clark Door systems.
only reason these cars were not succesfull was they used parts from manufacturers that wanted to shut down those components.
Yes one of reasons the M1's are scrapped and not rebuilt, if a 10 year overhaul would have been done the purchase of components would have been enough to keep production of those parts going.

Dutchrailnut:

That acceleration seems slow to me. After 40 years of wear and tear, a new, higher hp engine with ac motors, computer controlled adhesion control, etc. I would expect the Genesis to do better. I can't remember, but doesn't the FL9 have 1750 hp for traction? What speed were the FL9s geared for?

The FL9's were geared for 83 but allowed 89 mph. yes a FL9 has 1750 for traction and a seperate HEP engine.
A Genesis has 3200 hp but about 100 hp per car goes to HEP.
so on a 7 car train you only got 2500 for traction.
now figure in the 25% loss in gearing for being geared to high.
Same with a single DE/DM after the HEP there is not much left for traction.

Everyone: Interesting debate here! Good pros and cons on both sides. I remember being told that the LIRR always had to be different when it came to rolling stock regarding the C3 vs. Comet debate. I personally thought that the MBTA bilevels would have been good for the LIRR but for one thing: From reading fact sheets on both cars the MBTA car is one foot taller than the LIRR car-all the difference is right there why they cannot run on the LIRR. I was against putting high platforms everywhere as un-necessary. To me a station such as Southold is a classic example of this. Back in the early 80s and before,Bay Shore was the first station to get full 12-car high level platforms in diesel territory. I recall that at one time only Richmond Hill was the only diesel-only station that had high platforms and Hicksville originally until electrification (1962-1970) was the only major station in diesel territory with them. I do not like the Genesis percolator(My nickname for them because of the gurgling noise they make) front ends or the DE/DM front ends either-the design and colors could be better-but as for new engines NJTs PL42 is not bad. The NJT bilevel car for what I have seen is a attractive car inside and out. One person here mentioned interior sightlines-the M7 car does NOT have good visibility inside at all-especially the restroom-equipped cars. Some memories and thoughts from MACTRAXX