Just got dyno tuned, couple q's

[Blenderhead]

I just got my MarkVIII dyno tuned. The only mods are a 5-speed swap, cobra intake, and straight pipes in place of the stock mufflers. It put down 252hp and 263ft-lbs, which I thought was pretty good based off what I'm seeing from other mostly stock MarkVIIIs. What is confusing me though is where it made peak hp, it was only about 5000rpms! Shouldn't this motor make peak hp a lot higher than that? The hp curve stayed pretty flat from 5K all the way up to 7K when they shut it down, but was slowly dropping off after 5K. What rpm do MarkVIIIs typically have peak hp around?

 

[Rich88LSC]

Yes typically they peak higher especially with the Cobra intake. Weak fuel pump maybe?

 

[Blenderhead]

Maybe, it does have 145K on it. I'll have to double-check the sheet when I get home, but I think the air/fuel ratio stayed pretty constant as the rpms climbed, and if that were the case I would think it would show it start leaning out. What rpm do they usually peak at?

 

[driller]

It put down 252hp and 263ft-lbs, which I thought was pretty good based off what I'm seeing from other mostly stock MarkVIIIs.

That goes to show how much HP the automatic transmission sucks from the flywheel.

I'm not sure but I recall 5400 or so being the usual peak rpms for HP.

 

[Blenderhead]

One thing occurred to me driving the car today; I think my throttle cable needs to be adjusted because the pedal is notably higher than it was before the cobra intake swap, so maybe on the dyno run the throttle was going past all the way opened, and becoming a restriction again. I checked the dyno graph again, and the air/fuel ratio never went higher than 12.9:1 all the way up to 7K, so I don't think it is a fuel issue.

 

[driller]

Can the throttle blades over travel??? I thought they had stops and a spring extended with any over travel from the throttle pedal/cable. I don't know how the Cobra setup is actually though.

Best to have someone mash the go pedal and check the throttle blades though to make sure they are 100% open at WOT.

 

[Blenderhead]

Yeah, I'll be checking that on Sunday. I'm using the MarkVIII throttle body mounted on the cobra manifold, but it is the gen2 throttle body. I know what you mean about the gen1 throttle having the stops, but I don't think the gen2 does. I guess I'll find out on Sunday. I do know that right now the pedal is much higher inside the car, so we'll see.

 

[LaserSVT]

So am I reading this right? The 5-speed has so much less parasitic drain that its good for about 20 hp to the wheels? Gonna have to do some research on whats needed for the conversion then.

On my Gen2 I cant make the blades go more then half way.

 

[driller]

So am I reading this right? The 5-speed has so much less parasitic drain that its good for about 20 hp to the wheels? Gonna have to do some research on whats needed for the conversion then.

I don't know of anyone who has before/after dyno sheets, but yes the manual has significantly less parasitic losses.

 

[Roadboss]

You have to keep in mind that you are talking about a chassis dyno that is measuring output at the rear wheels. When you start trying to compare torque/HP curves of each setup you are comparing oranges and apples using this method. In trying to optimize each you need to look at a whole bunch of elements i.e. (cams,timing,tire size, final drive ratio,torque converter),