Rpm limit question

Adam Vinnicombe

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Hi all want is the upper safe rpm limit on the PI 2v?
I believe I was told 6000 rpm but today I loaded a new tune into the new edge and was not aware that the new tunes rpm limit was set at 7,000 rpm, anyway I noticed that the car was still pulling strong very strongly at 6,500 and above so why is the stock limiter set so low when the engine is still pulley strong at 6,500 plus rpm?
Is it due to weak rods, crank flex or something else?

PS I only took it passed 6,500 three times which the data logs saying I hit 6730 as a max, hopefully I’ve not broken anything
 

07GtS197

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You can rev the shortblock to around 7k but there’s no point to as the stock cams and heads stop flowing around 5500. Then you have to worry about the oil pump gears and transmission.


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96blak54

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The intake manifold is the choke point. Oddly the pairing of stock cams along with pi valve train, potential beyond 6k rpm is possible by the means of valve float. The heavy valves and reduced seat pressure gonna be slow to move at them rpm giving more open time, just like a performance cam would. But im not saying the stock will perform like the performance cam.

Id say spin it! If it will do it, roll with it. Keep the oil change intervals low and use top dollar stuff. Motorcraft oil filter. Nothing greater than 5w20.
 

lwarrior1016

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agreed

my redline is 7100, but i have a built engine that likes being up there.

its been said this engine has turned 8400 rpm as well

but who can really trust @lwarrior1016
The only thing I trust is my datalog that says it’s been there. I wanted to see if it would come from together.
 

lwarrior1016

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If I’m not mistaken, the ecu becomes an issue at high rpm like that. I don’t know this for a fact but I thought I remember reading that the stock computer doesn’t like going over 7k rpm.
 

Adam Vinnicombe

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Thanks for the replies
The reason I’m asking is because I’m trying to figure out the best way to drive her to get the fastest acceleration out of her. As in should I red line it in every gear before changing up or change up before red line. Now I don’t have a rolling road near me to see where the torque band is on my car so been trying something an old man told me what he used to do back in his days.
Anyway what he told me was to put the car in 2nd gear start rolling at a set speed and then floor it and where the rpm/mph start to rapidly climb is the beginning of the torque band and when they start to slow that’s the end, then to use this information to figure out when to go up a gear and be in the power band.
Anyway this is what I did, 2nd gear 2,000 rpm (which is 20 mph) then went to WOT the car accelerated Nicely up to 3000 rpm then the wheels break traction , done the same in 3rd and once again great acceleration up to 3,000 rpm and the back end looses traction again . So by this I’m guessing my power band starts at 3,000rpm. Now to the next bit the old man told me witch was to see when the acceleration started to slow, well thats the problem in 2nd,3rd and four gear the acceleration showed no sign of slowing down and I had crossed the 6,500 rpm range.
Anyway when should I be changing gear to get the fastest acceleration in a straight line out of the new edge ?
If my torque/power band is starting at 3,000 rpm when I change gear do I want the rpm to drop down to the beginning of the power band (3,000 rpm) or higher up in it?

im running the following mods
Long tube headers
Full de-cat
UDPs
CAI
75 mm throttle body
75mm trick flow plenum
Aluminium prop shaft
Lightened flywheel
4.10 gears
Diablosport 93 octane tune
 

96blak54

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There becomes an rpm point when ignition timing becomes moot and autocombustion comes into play. We thing spark timing plays a roll in this area, but when rpm are high making crazy piston speed, igniting fuel with a spark becomes a slow process. This is when auto combustion needs to play a roll. Cylinder temperature along with all the forces of compression destabilize the fuel into a forced combustion and at them speeds actually becomes very controlled. Messing around with octane grade and mixture content opens a new door. All this of course means no restrictions with the intake track.
 

Adam Vinnicombe

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So when changing up a gear when racing I want the rpm to fall down to around 3500 rpm to get the most out of each gear?
Also I’ve been practicing my launches.
Now on my mates new edge which has the stock gearing I can launch pretty good at 2,500 rpm and my first to second shift are good but the down side to the stock gearing is that 3rd and above are slow gears when compared to my new edge with the 4.10 gears BUT I’m having massive issues with launching with my 4.10 gears is there some tips to a good launch with the 4.10 gears with out just wheel spinning?
 

Randall Garner

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Are you thinking for drag racing,. What class do you think you'll run. Drag racing is about consistency. Whether your a 20 second car or a 5 second car. Find a launch rpm where you do not spin off the line. If that means a set of good quality drag radials so be it. You are also looking for realibility if ya drive to the track , you want to drive it home. So if the car is pulling hard at 6000 and your next shift puts you back in the torque range , and your not hurting the car. I would run it there until your comfortable with iit before increasing rpm . you may find out your nearly as fast as lower roms than running it to redline. I have a friend with a 03 mach1 shifting at 6 all stock, it ran 13.8 when he trued to raise rom to redline he only gained .2 seconds. And was putting more wear on the car. He was launching around 2500.
 
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There becomes an rpm point when ignition timing becomes moot and autocombustion comes into play. We thing spark timing plays a roll in this area, but when rpm are high making crazy piston speed, igniting fuel with a spark becomes a slow process. This is when auto combustion needs to play a roll. Cylinder temperature along with all the forces of compression destabilize the fuel into a forced combustion and at them speeds actually becomes very controlled. Messing around with octane grade and mixture content opens a new door. All this of course means no restrictions with the intake track.

...umm


wat
 

Burninrock24

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If you have a dyno sheet, you want to shift at the level that gives you the most area under your HP curve in your current RPM and into your next gear change. The redline is more idicitive of when the engine runs out of air vs when it starts to self-destruct. That said, anything sniffing 7000 I would start looking into at least balancing the rotating assembly. But unless there's strict requirements to remain stock, at that point I'd rather just buy better internals.
 

Adam Vinnicombe

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If you have a dyno sheet, you want to shift at the level that gives you the most area under your HP curve in your current RPM and into your next gear change. The redline is more idicitive of when the engine runs out of air vs when it starts to self-destruct. That said, anything sniffing 7000 I would start looking into at least balancing the rotating assembly. But unless there's strict requirements to remain stock, at that point I'd rather just buy better internals.

I’ve now found many dyno sheets for stock and slightly modified 2v new edges and have worked out roughly the best time to change up into the next gear so going to be giving that a go soon. But I can’t wait to get a dyno run done on my actual car just to see what power she has and where in the rpm range it is.
Thanks everyone for all your help :)
 

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