Why is a L18 different from a L18 ?

[Eriks]

Hi all,

 

Perhaps someone can explain the difference in hp between a L18 in a 610 (105hp) and a L18 in a 910 Bluebird (88hp) ?

 

 

 

 

[flatcat19]

910 is a bigger, heavier car.

Maybe supplied options lowered hp rating also.

 

 

I'm not sure as to specs/year of a 910-

but I want to think that there was a change in how hp ratings were measured back then also.

[MikeRL411]

Because the 910 was sold to old farts like me who had forgotten the difference between the brake pedal and the accelerator.  The lower HP rated engine made a smaller hole in the Liquor store window and front door.

[Sealik]

 The lower HP rated engine made a smaller hole in the Liquor store window and front door.

 

Pfttt...no problem

Just have to enter sideways with a little more momentum .... :D

[Ranman72]

maybe a different head lighter cam 

WHY ? 

I have no Idea 

[datzenmike]

Simple.... when the 610 was around the motor was rated in engine horse power. That's power right from the crankshaft, usually with no alternator, no muffler, no water pump, no pollution air pumps, no fan, transmission or diff, or any parasitic losses what ever. The public got tired of cars with big hp numbers that preformed poorly in the real world so the rating was changed to Net horse power measured at the wheels with all drive train losses accounted for.

 

Very roughly a rear wheel drive vehicle looses around 17% to frictional losses in the tranny and differential. And 105 minus 17% is... 87 hp so this number is fairly close.

 

My L20B in my '76 710 is 110hp which is about 90 real world hp on a good day.

[Eriks]

Thanks for the replies. It sounds like a L18 is in fact the same as a L18 :)

 

That is, if it wasnt for the "S" at the end of the L18 in the 910. I read somewhere that the S stood for "single carb" while a T would mean "twin carb". Still I wonder what makes a L18S different from the original L18 in a 610. Hmm

[datsunaholic]

A 910 would have used a 2nd or 3rd generation block, though that had nothing to do with horsepower.  The L18S designator was to distinguish it from the L18E, which used a different head machining.  L18T blocks weren't marked as such until much later, if ever.

[datzenmike]

 
 
 

sorry for the crude photos... this is the block from my 1989 Nissan Hardbody. It's engine number is "L18S 254905R" stamped on the block. It's the standard engine in 1800cc South African Hardbodys. It came with V912 head, 4cc dished pistons (85mm), Nikki carb, distributor with points! You could say the ideal L motor setup for a beginner to learn on - with the help of legendary virtual mentors like Hainz and Datsunmike...

Could be just a later new casting. Here's some info on the L18S

http://community.ratsun.net/topic/49463-l20s/

[Ranman72]

Simple.... when the 610 was around the motor was rated in engine horse power. That's power right from the crankshaft, usually with no alternator, no muffler, no water pump, no pollution air pumps, no fan, transmission or diff, or any parasitic losses what ever. The public got tired of cars with big hp numbers that preformed poorly in the real world so the rating was changed to Net horse power measured at the wheels with all drive train losses accounted for.

 

Very roughly a rear wheel drive vehicle looses around 17% to frictional losses in the tranny and differential. And 105 minus 17% is... 87 hp so this number is fairly close.

 

My L20B in my '76 710 is 110hp which is about 90 real world hp on a good day.

should have known 

Mike knows everything  :w00t:  :w00t:  :thumbup:  :thumbup:  :thumbup:

no really that makes total sense and I believe you are correct 

 

would this 17% be approximately the same kind of loss on a performance built motor one that is ported etc or would that percentage be less 

[ggzilla]

Auto makers to this day rate HP at the engine.

 

The big change was to Net HP. This occurred in 1972 for the American auto industry. Prior to about 1972, SAE gross hp ratings (aka bph - brake horespower) was used. This was the engine without accessories and was was not standardized, so different manufacturers rated it differently. Since 1972 in America the Net SAE rating has been used per standard J1349. This is the engine with all accessories (alternator, air cleaner, etc) as fitted in the car, so it is more realistic. Both SAE net and gross ratings are based on an engine dynamometer (not a rear-wheel dyno). The "brake" is referring to the dyno's putting a retarding force on the engine.

[datsunaholic]

Correct.  Otherwise, if they were measured at the wheels, the HP rating would be different based on what transmission (especially in the early 80s when automatics had as much as 15% more loss than the manual).  But the dataplate and MFG HP ads don't differentiate for trans or rear gear options.  Nor do they include optional accessories like A/C or power steering.

[dr.feltersnatch]

putting a retarding force on the engine.

 

 

i have done that once or twice :rofl:

[MikeRL411]

 

would this 17% be approximately the same kind of loss on a performance built motor one that is ported etc or would that percentage be less 

 

The loss is inherent to the transmission and rear end efficiency and has no bearing on the input.  A 1000 HP engine or a 96 HP engine would have the same efficiency loss if the 1000 HP engine didn't strip the gears and blow the U joints.