View Full Version : Long rod motors?
Pushit2.0
08-11-2005, 10:08 AM
I just thought we should talk about this a little more. So what, if any, tested information do we have on this. I have 2 sets of Crower rods for my car, normal and 6mm longer rods. I was going to come up with a way to test the two sets, keeping as much the same as possible. With the longer rod you need to get custom pistons that moves the pin up in the piston, giving a better rod ratio and more dwell time at TDC. What do we think on this?
~John
I am running a 2.0 still also
Pimpin Dsmstyle
08-11-2005, 10:19 AM
Ironically, I was just talking about this with someone last night. I was going to create a post but I didn't know what to say. I don't know much about it but I would like to.
If people could, could we have information added newb style? I want to be able to understand. good call John.
The longer rods will give the rod a shallower angle. This reduces side load on the pistons, and as John stated, increases the dwell time. Dwell time is good in an NA application, you can make more power. In a FI engine with high boost, it is not desirable since we are fighting detonation and that gives more time for detonation to occur.
The rod ratio of the 2.4 is 1.5 and the long rod version is 1.56. 1.7 is considered ideal for a NA engine. I really don't see a big enough difference with the long rod version to warrant the extra cost. It is less than a 10% difference in rod ratio and there are some bad effects too.
Shane@DBPerformance
08-11-2005, 11:08 AM
I am not sure why you would want a longer rod on a 2.0, unless you want to rev it like a motor cycle. It already has a 1.69 rod ratio, which is quite good. With that and the 88mm stroke, you should be able to rev to 9600 with off the shelf parts. Most of the guys reving higher than that are running aluminum rods.
Jakey
08-11-2005, 11:25 AM
So what justification does Marco use for his long rod shortblocks?
SlowWhite
08-11-2005, 01:43 PM
Also do you have to change anything on the motor as far as Oil goes? Talked with my brother about this for like 2 seconds and he mentioned that on his built MR2 Motor that he plans to rev the car to I think he said 8K (but anyrated point is) that he also mentioned he had to have something done to his oil pump in order to keep the flow of the oil up enough to handle the higher Revs? Or at least I think that's what he said. (again really quick conversation, didn't go into depth)...
Just thought that might be why guys like brent go with a Dry Sump system.
So what justification does Marco use for his long rod shortblocks?
He's canadian?? He sells them saying you can rev them higher than a regular rod 2.4.
A dry sump system prevents foaming of the oil and also allows the engine to be mounted lower in the frame to lower the CG.
mastadonic
08-11-2005, 03:21 PM
it also cuts parasitic drag since the crank doesn't have to plow through all that oil anymore
Pushit2.0
08-11-2005, 03:54 PM
So for a turbo motor you want the rod ratio lower then a NA motor, so the piston is not at TDC as long. I planned on reving my motor as high as possible, a few things like power band, trap speed will help me deside how high I should go. 9600 might be high enough I do not know.
~John
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