View Full Version : raising rev limits F7R
hi guys
i have a question regarding the rev limit on the F7R engines.
1. what should be done to the head so the engine could rev higher then the std rev limit? springs, retainers ect ect...?
iirc ive seen a williams in greece that was revin about 8k without any problems.
2. would you gain any thing if these engines would set to rev higher then the std rev limit?
i hope you guy understand my question.
cheers
dhayrone
On a standard engine, a rev limit to 8k would be pointless as the internals cannot benefit from it. With forged components, a different cam profile and maybe some lighter components in the head, such as valves, you could begin to explore the higher rev ranges.
robi1000
04-02-2011, 15:07
First of all you need forged bottom end (especially forged rods). That will break before top end will.
If you want to upgrade your head it will cost you a lot. You might want to buy uprated valve springs (around 400€ iirc) and retainers (again around 400€). If you want to go gardcore, a new set of titanium valves should do (about 800€), but then you need bronze/beryllium valve seats and new valve guides (about (350€ + new guides).
You will also need suitable cams with the profile suited for such high revs. Regarding power... Power is a function of torque and engine speed. Higher engine speed equates to more power (if torque stays the same).
I hope this answer was helpful.
ok tnx gus
i forgot to say that is for a turbo'd F7r.
last time i RR it pulled out 326Nm torque iir and 246 HP @10psi
i have forged low compr pistons but STD rods... it dont ness need to go 8k but surelly above the std 6000ish rpm a williams engine makes.. lets say if i can get enough power around 7.5k would be nice...
what do ya'll think?
Well, it's revs that break rods so for mad high you'll want them uprated as Robi said.
You can rev a stock F7R to 7,200 RPM (as per the 1.8 16v) without any immediate issues.
When have you hear of an F7R bending a rod due to rpm under 8k......
robi1000
07-02-2011, 00:37
Well, bottom line, BE will usually explode before valvetrain. :)
so 7.5 would be fine with std rods i guess.... ?
Laine_16v
08-02-2011, 21:12
I reckon you would be fine to 8k aslong as you had some ARP bolts on the rods tbh.
He forgot to mention that those are wheelfigures, meaning 280 at 10psi at the fly.
:lol:
Dont change it dhay, its fast as f*ck, you will brake it !
they dont do @ the wheel figures.....its a figment of imagination....ask laine.
right, over whe always talk about wheelpower (real power) and no pub-power (flywheel).
Dhay's car is custom mapped at Tovami dynocenter in Holland (Goes) by Fastchip.
I was reading the figures from the other guy's, all engine/fly and thats the reason why i mentioned it. No more, no less.
Laine_16v
09-02-2011, 09:03
they dont do @ the wheel figures.....its a figment of imagination....ask laine.
Wheel torque isnt recorded genearlly like i said, its calculated back to fly torque by using the gearbox ratios.
http://i652.photobucket.com/albums/uu244/deanoblad1/Clio172dyno001.jpg
That graph shows you an aexception of a 172 on the rollers see the normal power, bu the torque measured at the wheels shoots up into the many many hundreds.
all figures must be accurately recorded from the wheels to get accurate fly figures. whether it be torque or power. the only thing in contact with the measuring device, the r/r, is the wheels. this is why tyre pressure/compound csn make massive differences to the readings. only way to get true at the fly figures is to get the engine out and in a dyno cell.
right, over whe always talk about wheelpower (real power) and no pub-power (flywheel).
Dhay's car is custom mapped at Tovami dynocenter in Holland (Goes) by Fastchip.
I was reading the figures from the other guy's, all engine/fly and thats the reason why i mentioned it. No more, no less.
yes mate, i agree completely. wheel figures are where its at, no guessed fly figs calculated to make the cust happy ;)
and then you got people/dyno's/rolling roads, who calculate 15 till 20% drivetrainloses on the JC5 gb. :lol:
12.5% will be more then enough.
Laine_16v
09-02-2011, 19:11
all figures must be accurately recorded from the wheels to get accurate fly figures. whether it be torque or power. the only thing in contact with the measuring device, the r/r, is the wheels. this is why tyre pressure/compound csn make massive differences to the readings. only way to get true at the fly figures is to get the engine out and in a dyno cell.
Yes, but please read below as like i said, "torque at the wheels" means nothing....
You load a car onto the rollers you put it in 1st gear, you put your foot the floor, the rollers would spin up at a tremendous rate.
On the contrary put it into 5th gear and do the same, it would be sluggish and take a lonnnnggg time.
THe engine has stayed the same, yes? But what the rollers "see" between those two runs would be two very different torque outputs, agreed, yes?
That is because your gearbox is multiplying the torque output driven by the engine, yes? 1st gear gives a large amount of torque, 5th gear doesnt, yes??
So how can you possibly measure a torque output from the engine when the gearbox directly affects it? This is obviously why rolling road operators firstly run the car in the gear ratio thats generally closest matches actual engine speed, usually 4th gear yes? So approximately 1 revolution of the wheel, will equate to 1 revolution of the engine, still with me?
But 4th gear wont neccesarily be matching the engine speed (not every gearbox has the same 4th gear ratio afterall!), so a final divison will be made, the operator will hold the car in 4th gear at say 2500rpm. The RR computer will calculate wheel speed and RPM and make a final calcualtion that will mean it can figure out accrautely the engine torque at every wheel speed in 4th gear.
So do you understand when you see a normal RR graph that the torque figure on that graph will have been put through many dividing calculations taking into acount all of the above.
Saying the the RR graph has 125ft lb's peak at the wheels and then saying well must be about 150ft lb's at the flywheel is just completely farcial.
PS this isnt an arrogant post or anything i just wanted to fully explain it :P
descent modern RR's have a calibration system !
all figures must be accurately recorded from the wheels to get accurate fly figures. whether it be torque or power. the only thing in contact with the measuring device, the r/r, is the wheels. this is why tyre pressure/compound csn make massive differences to the readings. only way to get true at the fly figures is to get the engine out and in a dyno cell.
Yes, but please read below as like i said, "torque at the wheels" means nothing....
You load a car onto the rollers you put it in 1st gear, you put your foot the floor, the rollers would spin up at a tremendous rate.
On the contrary put it into 5th gear and do the same, it would be sluggish and take a lonnnnggg time.
THe engine has stayed the same, yes? But what the rollers "see" between those two runs would be two very different torque outputs, agreed, yes?
That is because your gearbox is multiplying the torque output driven by the engine, yes? 1st gear gives a large amount of torque, 5th gear doesnt, yes??
So how can you possibly measure a torque output from the engine when the gearbox directly affects it? This is obviously why rolling road operators firstly run the car in the gear ratio thats generally closest matches actual engine speed, usually 4th gear yes? So approximately 1 revolution of the wheel, will equate to 1 revolution of the engine, still with me?
But 4th gear wont neccesarily be matching the engine speed (not every gearbox has the same 4th gear ratio afterall!), so a final divison will be made, the operator will hold the car in 4th gear at say 2500rpm. The RR computer will calculate wheel speed and RPM and make a final calcualtion that will mean it can figure out accrautely the engine torque at every wheel speed in 4th gear.
So do you understand when you see a normal RR graph that the torque figure on that graph will have been put through many dividing calculations taking into acount all of the above.
Saying the the RR graph has 125ft lb's peak at the wheels and then saying well must be about 150ft lb's at the flywheel is just completely farcial.
PS this isnt an arrogant post or anything i just wanted to fully explain it :P
tnx for the post mate !!! appriciate it ...
He forgot to mention that those are wheelfigures, meaning 280 at 10psi at the fly.
:lol:
Dont change it dhay, its fast as f*ck, you will brake it !
@JO
dont forget what happend at the and of the runs at 10 psi when we were tuning it. a blown coupler so we could not up the boost to 15 psi. :(
so what i want is 15Psi and the engine revvin at about 7.5K
should be devil-ish .....
you know the date, march 26, then whe got another mapday. :D Check RTC dynotopic.
will be around august as im not in holland for a while
all figures must be accurately recorded from the wheels to get accurate fly figures. whether it be torque or power. the only thing in contact with the measuring device, the r/r, is the wheels. this is why tyre pressure/compound csn make massive differences to the readings. only way to get true at the fly figures is to get the engine out and in a dyno cell.
Yes, but please read below as like i said, "torque at the wheels" means nothing....
You load a car onto the rollers you put it in 1st gear, you put your foot the floor, the rollers would spin up at a tremendous rate.
On the contrary put it into 5th gear and do the same, it would be sluggish and take a lonnnnggg time.
THe engine has stayed the same, yes? But what the rollers "see" between those two runs would be two very different torque outputs, agreed, yes?
That is because your gearbox is multiplying the torque output driven by the engine, yes? 1st gear gives a large amount of torque, 5th gear doesnt, yes??
So how can you possibly measure a torque output from the engine when the gearbox directly affects it? This is obviously why rolling road operators firstly run the car in the gear ratio thats generally closest matches actual engine speed, usually 4th gear yes? So approximately 1 revolution of the wheel, will equate to 1 revolution of the engine, still with me?
But 4th gear wont neccesarily be matching the engine speed (not every gearbox has the same 4th gear ratio afterall!), so a final divison will be made, the operator will hold the car in 4th gear at say 2500rpm. The RR computer will calculate wheel speed and RPM and make a final calcualtion that will mean it can figure out accrautely the engine torque at every wheel speed in 4th gear.
So do you understand when you see a normal RR graph that the torque figure on that graph will have been put through many dividing calculations taking into acount all of the above.
Saying the the RR graph has 125ft lb's peak at the wheels and then saying well must be about 150ft lb's at the flywheel is just completely farcial.
PS this isnt an arrogant post or anything i just wanted to fully explain it :P
i dont think anyones disputing that are they?
all im saying is that to get an accurate calculation for torque at fly, you need an accurate figure to calculate from. whether it be run in 3rd 4th or 5th gear, the r/r will calculate from an 'at the wheels' figure will it not? i personally would rather take the at the wheel figure than at the fly. as u rightly say, the box will change this output until a 1:1 ratio is achieved. which would then make the wheel figure pretty much exact, of course there will always be friction losses, transmission losses, call them what you will.
as above. the only way to get truly accurate figures is to put it in a dyno cell.
I wrote a very long article about chassis and engine dynamometers on my homepage. I think every theory explained in this article (how does it work, inertia vs. stacioner dynos, chassis and engine dynos, correction factor, losses, why it's carried out in direct gear (or the closest gear to 1/1 torque conversion, 4th gear usually), forces on the rollers, single roll vs. tandem roll etc.). Try to translate it, it's written in Hungarian:
Dynamometers (http://www.fw.hu/yanooka/dpa_teljesitmeny_1.html)
Power and torque measurement (http://www.fw.hu/yanooka/dpa_teljesitmeny_2.html)
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