I guess that I may be used to my V-8's in my other vehicles that turn aprox. 1,500 RPM at 60 MPH. Is it normal for my Crossfire with automatic to be turning 2,200 RPM @ 60 MPH in "D" drive.

 

It has nothing to do with size of the engine...it's all in the gear ratio.

 

BWA HA HA HA HA...size doesn't matter!

 

Thanks for your reply. I understand about the gear ratio and engine size. What I'd like to find out is 2,200 RPM @ 60 MPH normal for an automatic Crossfire roadster?

 

I tell my wife this all the time!

 

Too funny, Pat!! It's not how deep you fish...it's how you wiggle your worm!!!

Anyway, back on topic...Chuck65 that sounds about right, but I have the 6 spd so I cannot confirm that for you for sure. I think you will probably get a confirmation here pretty soon.

 

Chuck, mine is about the same. With the mpg these car get i wouldn't worry about it.

 

you're right v8's turn slower because they have two extra pistons, and that gives the engine more usable torque at a lower rpm, so you have to rev a little higher to make the same amount of hp and TQ with the v6. also you have the 5 speed trans, not sure but I know SRT6 has a numerically lower final drive in the diff. as compared to the limited crossfire. Hey maybe you can figure out a way to swap in the slk350 6 seed auto.
I'll have to see what my standard trands revs at in 6th gear @ 60 mph.

 

I have to disagree with that statement. A revolution is a revolution, no matter how many pistons you have. The crank is going to move every piston it's full travel each revolution.

 

v8 can turn slower and make the same power of a v6 operating at higher rpm because of the 2 extra pistons. since Hp if a function of TQ and rpm. the v8 has more leverage and makes more TQ at lower rpm.

 

Now, that I can agree with (but, having two more pistons does not, in itself, make a V8 turn slower).

 

Great answer Maxwell. Thank you. Much better information than the above "pen*s" answers.

Chuck65

 

I have to disagree with that - take a current F1 V8, at 2200 rpm it would probably stall in a Crossfire. It's more about displacement - a larger capacity V8 will have more torque at lower revs and perhaps not rev as high, the 2.4L Honda V8 revs to 19,000 rpm.

I if we assume all the indicudual cylinder displacements etc are the same, ie the V8 has 33% more displacement that the V6 the statement is OK.

PS - 2,200 sounds about right - puts the revs at 2,570 for 70 mph and around 5,700 for 155 mph? Might even be a little on the low side, have to check next time i go out - probably at 60 or 70, not 155.

 

You are absolutely correct Maxwell.

I was only inquiring to see if others had the 2,200 rpm @ 60 to see if maybe I had a different rear end ratio than standard.

Thanks again.
Chuck 65

 

trying to compare apples with apples, a higher cylinder pressure is what makes the torque higher, if you have more cylinders as in a v8 v.s. v6 then you have more TQ in the v8 assuming both have similar cylinder pressures. the v8 has the extra leverage on the crank also.

that 2.4L v8 doesn't make enough cyl. pressure at 2,500 rpm to move anything, but a 900 lbs race chassis.

 

Now you guys are getting in-depth enough to start thinking about swept volume and rotational mass.

 

Welcome to a great forum Chuck65. Some have a sense of humor...some don't. I will reserve my answers for you in the future. My first response to your question was dead on...a couple of others just for fun. Sorry to offend.

 

wow the automatic runs the same speed and the stick!

my 6 spd is dead nuts at 2,200 rpm @ 60 mph, though I would love to get my hands on an SRT read diff, would make 1st gear a little longer in the legs.

 

I know you know V8's don't automatically have more torque - just making the point for any with less knowledge - get sort of fed up with people thinking a V8 is the only proper engine.

What as the last line for though - torque is leverage, for equal cylinder displayements etc the V8 doesn't have any more leverage per cyinder.

Anyway. what do I know - I6's win my heart (straight 6).

 

2,050 rpm @ 60 mph and 2,400 rpm @ 70 mph probably the difference because of the SRT gearing.