So what are these m50/m52s like then.

[oakey]

Oakey you're not too far from me I'd imagine (says Surrey under Location), I'm happy to meet up for a 'scientific test' one night if you fancy.

Why not. It would be fun me thinks. My tech1 is pretty light aswell

[ste]

The graphs are meaningless to be honest dude compare the speeds of the M20 and the M52 runs on my graph.

M52 : 164MPH @ 6146 RPM
M20 : 173MPH @ 5662 RPM

Something doesn't add up... some jiggerypokery there I think!

[ste]

Why not. It would be fun me thinks. My tech1 is pretty light aswell

It's a date! Drop me a PM and we'll sort something out.

[burrows]

Oakey bet it feels better now with ms and will be even better with the tbs

[oakey]

The graphs are meaningless to be honest dude compare the speeds of the M20 and the M52 runs on my graph.

M52 : 164MPH @ 6146 RPM
M20 : 173MPH @ 5662 RPM

Something doesn't add up... some jiggerypokery there I think!

What does the mph mean steve? Obviously neither of our cars are geared to that speed?

[Jhonno]

actually they could be, but normally you can hit the rev limit in 5th due to drag

[ste]

As you say, those figures are impossible, but based on the data the RR programme has been fed it's calculating those speeds.

Remember a BHP reading on the RR is just a diaplay of a calculation the RR software does after consulting data fed into it.

Tell it the gearing is different, the ambient temp is different or any other number of relevant data differs and it will alter that calculation accordingly and what you get fed out is practically meaningless.

Ultimately they are just numbers on a bit of paper.

I'm not attempting to say that anything underhand has necessarily happened, it's just that to run a car properly you'd have to set the rollers for each run and input all the data relating to that car. This just doesn't happen. The fact of the matter is my car has a different gearbox, different final drive in the dif and different rolling diameter tyres for the before and after so even those factos alone make a comparison ultimately futile.

[Aleksandar]

What would be the fuel economy for a m50b25?

[Jhonno]

depends how you drive it..

[ste]

actually they could be, but normally you can hit the rev limit in 5th due to drag

Nope, mine is geared to do 141MPH flat out on the limiter in top and it does get there with ease (regularly ). It just can't do 164MPH, with the gearing it's impossible.

You should klnow dude, you gave me the link to this calculator:

http://www.gearboxman.co.uk/inforatios.html

in this thread:

http://www.e3024v.com/board/index.php?topic=76.0

[Jhonno]

Doh!!

Wasnt thinking about yours when i typed that..

What is your limiter?

[ste]

Not sure, 6.7k possibly? That's what I used for the gearbox calculator anyway.

My theory is that the rolling road operator ran the M20 in 4th (to achieve a 1:1 gearbox ratio). They then without thinking ran my M52 in 4th too as they are so used ot doing that with an E30, even though you need to go into 5th to achieve 1:1 with the E36 box I have. Hence the top speed for the M52 is lower at higher revs. Thus, the comparison is even more skewed.

[Jhonno]

hmmm.. interesting. I think i worked mine out using a 7750 limit (s50 tho) at 170mph (same box and diff..) altho i run larger dia wheels might explain it

tho the s50b30 runs a 7.5k limit..

some arp bolts and remap should see 8k+ tho

[ste]

altho i run larger dia wheels might explain it

tho the s50b30 runs a 7.5k limit..

Yep it's the extra 1k rpm and the fact I use 215/40/16s basically.

[Karan]

hmmm.. interesting. I think i worked mine out using a 7750 limit (s50 tho) at 170mph (same box and diff..) altho i run larger dia wheels might explain it

tho the s50b30 runs a 7.5k limit..

some arp bolts and remap should see 8k+ tho

does power carry on increasing after 7.5k on a s50... cos it seems to on most ///m engines

this is interesting as on my s38 power was still increasing at the limiter just over 7k, so maybe i can increase the rev limit??

[Jhonno]

yes i think it does, esp with remap.. helps if you maybe have some cams in there also..

[DanThe]

Heres my dyno plot



M50B25 Non Vanos

I get 25mpg most of the time but 30 is very possible on Mway at 70mph (dont see that very often )

Giving it the usual roundabout abuse around town and no more than 20mpg is to be expected

I would never go back to 12v wrongness...

Cant wait to go 2800cc now

And then 3000

[ricey46]

You only get 25mpg?? I get that with my M20, and thats giving it abuse too!!lol.

[oakey]

I can return 30mpg on motorway drives

[ricey46]

Me too.....

[DanThe]

You only get 25mpg?? I get that with my M20, and thats giving it abuse too!!lol.

M52 will do over 30 very easily

But does it even matter when considering the performance increase?

Usually raising the performance means a drop in the MPG, not this way it doesn't.

[ricey46]

Nah not really, just intreagued!!

[munky30]

...and the car down to 1000kg...

How you doing that dude?

I was going to make some lexan windows - fancy going halfs if I make some templates?

not sure.

Removing all the trim, doorcards, headlinging, rear carpet, seats (except lightweight bucket seat for me) has got it down to 1100kg ish (on a scrapyard weighbridge)

So I reckon welding up the sunroof and rear doors then removing the inner skins from the sunroof and rear doors, plus window/lock mechanisms. Then stripping front carpet, sound deadening, any wiring thats not needed, smaller washer bottle, single headlights conversion, dash (replaced with alloy thing, digi-dash and switches), removing bonnet latches, hinges etc etc should get me close.

If that doesnt cut it, remove all rear glass and go for the van look using alloy sheet. Lightweight wheels will help a lot but seeing as I use steelies for track they're not really that important.

And then, lexan front windows with a sliding hatch instead of opening and closing, and lexan boot window.

Ideally all that will get it far enough below 1000kg that a roll cage wont take it back over.

Who knows, its all guess work tbh.

[reggid]

Dont completely disregard a 2.7. Heres my chart: 12 less valves 100 less cc, standard cam. More hp at all rpms until mine drops off at about 5200rpm. And also considerably more torgue throughout the rev range.

ps. Im not trying to start an arguement, nor am I saying my engine is better than yours. Just thought it was an interesting comparison. Obviously the cars were tested on different dynoes etc etc

Yep it is an interesting comparison and you won't get an argument from me. The whole point of forums like this is interesting debates like this.

You have a very nice graph and torque curve, but I'd confidently bet you the V5 of my car that if your 2.7 M20 has a standard head and cam it wouldn't come close to making the same figures as my M52 on the same rollers.

As I said before I had an M20 2.7 with a proper Les Stannard bottom end, a sorted Griffin Motorsport head, Shrick stick in it etc., etc and it made less power than my M52 does now on the same rollers, plus the M52 despite being in a heavier touring shell gets up the 1/4 mile 1.5s quicker.

As M5 pilot says too, this is a standard M52 - with cams, verniers and management the M52 has got loads more potential.

You're also talking about a stroked M20 to get your 2.7, easy to take an M52 to 3.0l for a similar effect.

Don't get me wrong I love M20s, the sound, torque, smoothness, it's just that it's a few generations behind the M52 in development terms.

I'd be intersted to see the 2.7 vs m52 dyno plot if you have it? What did you trapspeed in the 1/4 as this tells power and performance potential when moving....a bit of wheel spin or poor track conditions can easily knock a 0.5-1sec away from the ET......

[reggid]

The M52 has a really good low end torque delivery due to the vanos. You tend to get much flatter torque curves with the M52.

I would agree but STE's graph seems to shows otherwise??

[M5pilot]

Ste,

The Bexley dyno measures BHP. The only figure that can be skewed is the torque figure as this is reliant on the speed vs rpm calculation to be correctly calibrated (manually). In this case it's obvious this has been incorrectly calibrated so ignore the torque figure.

The BHP figure is still correct even if it is at the wrong rpms.

[reggid]

Ste,

The Bexley dyno measures BHP. The only figure that can be skewed is the torque figure as this is reliant on the speed vs rpm calculation to be correctly calibrated (manually). In this case it's obvious this has been incorrectly calibrated so ignore the torque figure.

The BHP figure is still correct even if it is at the wrong rpms.

which graph are you talking about and where is the error?

[ian332isport]

The Bexley dyno measures BHP

No dyno can measure BHP directly. A dyno measures torque, and calculates BHP from it.

[JazzMan]

Here's some estimated flywheel figures from an M52B28 with the M50 manifold and BBTB before and after mapping:

Before:


After:


I'm building an M20B28 at the moment - the reason why is for the experience of doing it I could just drop an M52 into the car and get similar power but the cars a project so I didn't want to do that (I may still in the future from an S engine into )

[ste]

Ste,

The Bexley dyno measures BHP. The only figure that can be skewed is the torque figure as this is reliant on the speed vs rpm calculation to be correctly calibrated (manually). In this case it's obvious this has been incorrectly calibrated so ignore the torque figure.

The BHP figure is still correct even if it is at the wrong rpms.

Sal, any dyno can only measure torque. It is impossible to measure BHP.

BHP is just a result of a calculation performed on the torque reading the RR produces.

BHP = Torque (ft/lbs) x rpm/5252

It's why any RR graph that doesn't cross at 5252 RPM is utter nonsense.

So if the gearing is incorrectly calibrated on the RR, as you correctly state, the recorded torque result is incorrect. Input this into the above formula (a calculation the RR software is doing) and the BHP reading you get out is also incorrect, no way around that I'm afraid it's just simple maths.

[reggid]

Ste,

The Bexley dyno measures BHP. The only figure that can be skewed is the torque figure as this is reliant on the speed vs rpm calculation to be correctly calibrated (manually). In this case it's obvious this has been incorrectly calibrated so ignore the torque figure.

The BHP figure is still correct even if it is at the wrong rpms.

Sal, any dyno can only measure torque. It is impossible to measure BHP.

BHP is just a result of a calculation performed on the torque reading the RR produces.

BHP = Torque (ft/lbs) x rpm/5252

It's why any RR graph that doesn't cross at 5252 RPM is utter nonsense.

So if the gearing is incorrectly calibrated on the RR, as you correctly state, the recorded torque result is incorrect. Input this into the above formula (a calculation the RR software is doing) and the BHP reading you get out is also incorrect, no way around that I'm afraid it's just simple maths.

while they do measure torque to find BHP its not crank torque its ROLLER torque. Crank torque is always derived from BHP!

roller torque @ WOT & roller rpm -> roller whp
roller torque @ coastdown & roller rpm -> coastdown hp

roller whp + coastdown hp -> bhp
bhp & rpm -> crank torque

so Sal is right the bhp will be right and if the rpm pickup reads wrong the torque will be wrong. Its easy to check whether a graph is nonsense using the equation hp = tq x rpm/5252 just pick a point and check.

The only time the tq and hp curves cross at 5252 is when the units are in hp and ft-lbs (kw and nm cross at a different rpm) also scales and increments of the graph must be same.

The gearing is not input at all and actually is nearly irrelevant to the BHP output. As i said you measure torque to rollers and the speed of rollers this gives hp at rollers (whp), do this same thing during coastdown and add them to give BHP. Only once you know BHP and engine rpm (inductive pickup) can TORQUE be calculated.

So you have it all a bit backwards

[reggid]

Here's some estimated flywheel figures from an M52B28 with the M50 manifold and BBTB before and after mapping:

Before:


After:


I'm building an M20B28 at the moment - the reason why is for the experience of doing it I could just drop an M52 into the car and get similar power but the cars a project so I didn't want to do that (I may still in the future from an S engine into )

seems like a bit of funny business going on in the last graph .......AT16* and IT45* quite a big difference.........mmmh

[Ant]

good spot that man.

hike up the measured IAT and the rollers fiddle factor will show increased HP as it compensates for the power loss from the high intake temps.

spurious indeed.

[DanThe]

any RR graph that doesn't cross at 5252 RPM is utter nonsense.

So based on that statement my graph and the 2 JazzMan posted are incorrect?

[ste]

No, because they do cross at 5252 - it's just the scales are different, so they appear to cross at a different point.

Move the torque curve on those praphs to sit on the same scale as the power curve and they cross do cross at 5252.