300° BMW Motorsport cam

[Brams]

2 hours ago, Oldtimerfahrer said:

There are multiple other posts on this topic, one even includes some data as well...Seems that Schrick does measure differently.

The 300 degree cam is certainly not aggressive, even with 45's, higher compression and a ported head the driveability is quite ok and you can even get a decent idle if all else is good.

A.

That's the post I read to get to the conclusion that the BMW 300 cam is closer to stock than the 292, at around 280 degrees in Schrick measurements. 

 

However, it doesn't explain how the BMW 300 camshaft seems to get the same 160hp as the 304 at a lower RPM, when using the same parts (10:1, 45 DCOE etc)?

 

Just seems a little strange you get the same results with a cam with 20 degrees less duration, anyone have light to shed on that? There is very little on people actually dynoing the 300 cam to have concrete results.

[Oldtimerfahrer]

Hi,

Dynoing is one of the to-do's I never get to. I have the same configuration and dyno'd it once in 2006 when it had not been set up properly and only had 128 or 130hp at the wheels with small chokes and a lame Bosch distributor with a defective lobe....it runs completely differently today, but I haven't redone the measurements. 

A.

[Brams]

52 minutes ago, Oldtimerfahrer said:

Hi,

Dynoing is one of the to-do's I never get to. I have the same configuration and dyno'd it once in 2006 when it had not been set up properly and only had 128 or 130hp at the wheels with small chokes and a lame Bosch distributor with a defective lobe....it runs completely differently today, but I haven't redone the measurements. 

A.

Considering losses through the trans and diff, you're already quite close to 160 hp with the motorsport cam - it does look like the right cam for these engines. 

[jimk]

30 hp is 22.4 kW or 57,000 btu of heat that would have to be dissipated from the gearboxes and is 5 times more than a residential electric water heater has for heating elements!.  My propane wall heater at my cabin was only 30,000 btu.  I question the losses.  Some reality please.

Edited August 19, 2020 by jimk

[Brams]

16 minutes ago, jimk said:

30 hp is 22.4 kW or 57,000 btu of heat that would have to be dissipated from the gearboxes and is 5 times more than a residential electric water heater has for heating elements!.  My propane wall heater at my cabin was only 30,000 btu.  I question the losses.  Some reality please.

 

Unfortunately the transmission loss equation is a bit more complex than that. This is at 6500 rpm not idle, and both the differential and gearbox are sources of loss. There will also be some slip between the tyres and the rollers unless a hub dyno was used and all the bearings and CV's in the system will also have some loss. Within the diff and box there are three main types of loss, heat as you mentioned, then spin losses which is just the gears sloshing the oil around and then there's vibration. Vibration is mostly absorbed by the transmission/diff mounts. Spin losses can be significant- the paper in the first link measured a 2 kW loss at 3000 RPM pinion speed in a differential. Then there is the heat loss which you mentioned, which they estimate to be 4kW in just the diff at 3000 rpm. Compound this with most probably having old bearings and using old oil and there's a fair bit of loss in the differential alone. You can assume about 5% loss in the gearbox (second link), so with these figures the engine may have had 145 hp at the crank? Getting quite close to 160 hp on small chokes and a poorly functioning distributor don't you think? 

 

https://www.jstor.org/stable/26278193?seq=1
https://ep.liu.se/ecp/043/048/ecp09430059.pdf

[jimk]

Any slosh loss heats the gear lube, any power loss has pass out of the case as heat.

Impossible to heat my cabin with the heat of the trans and diff.  CV joints are virtually straight with the car on the ground, can't fathom any heat generated there.

Will believe he numbers when some actual numbers from calibrated engine and dynos are presented.  Before that, it's all street talk.

[Brams]

2 hours ago, jimk said:

Any slosh loss heats the gear lube, any power loss has pass out of the case as heat.

Impossible to heat my cabin with the heat of the trans and diff.  CV joints are virtually straight with the car on the ground, can't fathom any heat generated there.

Will believe he numbers when some actual numbers from calibrated engine and dynos are presented.  Before that, it's all street talk.

Slosh loss isn’t heat, it’s the energy spent moving the oil not the wheels, kinetic not heat energy. Otherwise agreed, but also the point of my earlier posts.. where are the dyno results with wheel power at! 

 

 

[jimk]

15 hours ago, Brams said:

Slosh loss isn’t heat, it’s the energy spent moving the oil not the wheels, kinetic not heat energy.

Anything that takes energy to make happen either passes the energy thru as work produced or it generates heat.  Seems like that's what the thermo class defined.

[Brams]

1 hour ago, jimk said:

Anything that takes energy to make happen either passes the energy thru as work produced or it generates heat.  Seems like that's what the thermo class defined.

The oil has been moved by a force and therefore work is done

 

300 degree BMW Motorsport cam dyno sheets anyone?

[mccusername]

Guys, please settle this once and for all. My car has a 300 Motorsport cam and I can't drive it until this slosh issue us resolved.

 

[jimk]

To get 160 hp at the crank and at a gasoline power conversion ratio of 0.55 lb fuel / hp-hr, 13.0 afr, 100% VE an rpm of 7.200 is required.  If redline is not to be exceeded, 140 hp is the best one can get at the crank.

Only the user can say if redline was exceeded for max hp.  I doubt the VE can make 100%.

 

Slosh rules are dictated by the gazinta rule,  What gazinta da box gotta come outa da box.  It can't disappear.

Edited August 20, 2020 by jimk

[uai]

2 hours ago, jimk said:

To get 160 hp at the crank ... an rpm of 7.200 is required. 

That‘s not true ( in real life with real world Parameters)  I‘ve 

been on the Dyno today 160 is possible below 6000 (it‘s a dyno known to be conservative). The Engine builder said 205 Nm could have been possible with a different exhaust header.

Edited August 20, 2020 by uai

[TobyB]

I can't do the black box emissivity for the boxes, but I can tell you-

 

at 6500 rpm with 150 ft/lbs and 175 bhp, the transmission doesn't get WARM.  It stays at

engine water temperature, and it is STABLE throughout a lap.  I think there are 

fractional horsepower losses in the trans.

 

The diff DOES get warm.  However, with a decent set of gears, it's usually under

250F.  And it is stable after 4-5 laps.

  Again, I don't know what a diff can emit in heat absolutely, but relatively,

that's not very much.  

I suspect it absorbs something well under 10 hp, average, and it's hard to calculate instantaneously,

as gear loading varies inversely with speed.

 

30bhp losses in a 2002 drivetrain would slag those little gearboxes- the diff weighs

only a bit over 50 lbs, and the trans a bit under.

 

t

the 300 cam is pretty mild...

[Lorin]

3 hours ago, TobyB said:

the 300 cam is pretty mild...

I helped a buddy of mine with the purchase of a very nice and very period modified ‘70 2002 in the early ‘90’s. 
 

The engine was high comp, stahl header, 40 dcoe and a 300 degree bmw cam. I was expecting a pretty radical car but it was completely docile and not massively different than my stock engine with a 40/40 downdraft and stahl header. 
 

I was surprised. 

[Brams]

4 hours ago, TobyB said:

the 300 cam is pretty mild...

 

43 minutes ago, Lorin said:

I helped a buddy of mine with the purchase of a very nice and very period modified ‘70 2002 in the early ‘90’s. 
 

The engine was high comp, stahl header, 40 dcoe and a 300 degree bmw cam. I was expecting a pretty radical car but it was completely docile and not massively different than my stock engine with a 40/40 downdraft and stahl header. 
 

I was surprised. 

 

So the 300 cam is pretty mild, there seems to be few drawbacks. 

 

The question then is how does it make what seems to be the exact same power as the much more aggressive Schrick 304?

 

The dyno sheet below is very healthy!

 

5 hours ago, uai said:

That‘s not true ( in real life with real world Parameters)  I‘ve 

been on the Dyno today 160 is possible below 6000 (it‘s a dyno known to be conservative). The Engine builder said 205 Nm could have been possible with a different exhaust header.

This is the 304 cam at the wheels. Again at approx 160 hp with a 10 hp loss like toby said. 

 

Which begs the until now unanswered question, why would you pick a schrick 304 over the bmw 300 cam (except if you're worried about the originality of the head with lineboring)?