Bullet Ride's 2.8L Stroker Project (Updated: Dyno Plot pg. 6)

[redlightpete]

Does the result of the cam timing change feel like your 'wishful speculating'? You'd think that you'd have noticed if the torque had dropped off as much between 3k and 5.5k as the dyno comparison shows. I'm interested because I'm putting together the same cam and motor setup and was just going to use a stock cam gear.

[Bullet Ride]

I went to a dyno day today held by a group of local BMW enthusiasts. I decided to put my stroker on the rollers again just to see what it'd put down on a different dyno. It's worth mentioning that earlier this year I had the timing belt off to do some work on the front of the motor and when I put it back on I retarded the cam timing by 4 degrees because based on my dyno results last year I felt as though it was a bit too advanced.

In order to get a scale of the numbers, there were a couple E46 M3s on the dyno today running in the 285whp range and a couple E39 M5s running in the 315whp range...

First run I ran the timing map I've been running all along, second run I tried adding some timing, third run I tried pulling some timing. Seems as though the timing map I had from the get go was pretty good.



For reference here is last years dyno plot again...



To get a sense of comparison between the shape of the power and torque curves with the advanced and retarded timing I plotted values from both graphs...



The magnitude of the numbers isn't really relevant since they are from two different dynos, but the shape is telling. The horsepower climbs better on the top end and doesn't drop off as drastically, the torque peak is shifted forward, the overall shape of the torque curve is a bit better and it also doesn't drop off as drastically on the top end.

I'm speculating that if I was on the same dyno that I ran on last year, the numbers would look more like this....



But that's just me doing some wishful speculating

[nando]

This seems like a really nice build for an M20. Does this make more power (peak or under the curve) versus an M52B28? It just seems like a lot of work for +45-50whp - not that I don't appreciate the build, because it's great!

yes. but an M52B28 is probably going to have 100,000+ miles on it, and if you just did a proper stock rebuild, would cost a significant sum. if you wanted to do an apples to apples comparison, then you'd have to rebuild the M52 to "brand new" as well, and the cost difference would be minimized significantly.

also, the M52 would still be stock and not have a standalone ECU that you can dyno tune.

[Bullet Ride]

It ended up costing more or less what I thought it would. However as you can see I did the majority of the work myself. If you were to pay a shop to build this motor for you, you'd probably be better off just buying a metric mechanic crate engine.

[Cinnabar325is]

This seems like a really nice build for an M20. Does this make more power (peak or under the curve) versus an M52B28? It just seems like a lot of work for +45-50whp - not that I don't appreciate the build, because it's great!

Just wanted to throw in a few reasons that I also built a 2.8 M20 as opposed to going 24v.

-originality
-a dressed up M20 is a whole bunch cooler looking than an M52
-M20s sound better than 24v motors (not that 24v's sound bad)

Those reasons may not be a big deal and for most people, not enough to justify the cost vs. hp increase, but it was enough for me.

[blasphemy101]

A 24v swap would obviously yield better performance/$ but there's not really anything for me to learn from doing a 24v swap because it's already a well documented process. My goal with this project was just to learn about building a motor because it's something I had never done before. I happened to already have an M20 sitting around collecting dust so that's what I decided to use for the base of my build, but at the same time I didn't want to spend the money to rebuild a motor and end up with stock B25 performance so I opted for the 2.8L stroker route.

That makes perfect sense. I was just curious about your motivation.

At some point, I would like to do something similar. Did you end up spending much more than you expected on this build?

[Bullet Ride]

This seems like a really nice build for an M20. Does this make more power (peak or under the curve) versus an M52B28? It just seems like a lot of work for +45-50whp - not that I don't appreciate the build, because it's great!

A stock M52B28 is rated for 190hp and 210lb-ft at the crank which is approximately 165hp and 183lb-ft at the wheels give or take. I'm not sure what the curve looks like for the M52B28 but for a good portion of my plot I'm above M52B28 peak numbers, so yes, this build is making more than a stock M52B28. However if you were to take an M52B28 do an OBD I conversion add S52 cams and headers it would probably be putting down around 220hp at the wheels.

Someone mentioned the same thing on another forum so I'll just quote what I've already said elsewhere...

A 24v swap would obviously yield better performance/$ but there's not really anything for me to learn from doing a 24v swap because it's already a well documented process. My goal with this project was just to learn about building a motor because it's something I had never done before. I happened to already have an M20 sitting around collecting dust so that's what I decided to use for the base of my build, but at the same time I didn't want to spend the money to rebuild a motor and end up with stock B25 performance so I opted for the 2.8L stroker route.

[tinkerputzer]

Wow can't wait to see it. Should be nice :)

Right now I'm actually thinking about building an ITB set up as a winter project, not because the car needs it per se, but because it'll look sweet*, it'll sound sweet**, and the throttle response will be sweet***



* might look sweet
** should sound sweet
*** could be sweet
lol

[blasphemy101]

This seems like a really nice build for an M20. Does this make more power (peak or under the curve) versus an M52B28? It just seems like a lot of work for +45-50whp - not that I don't appreciate the build, because it's great!

[Bullet Ride]

Fyi m50 throttle plate is 64.2 mm vs m20 60 mm if your planning to make your own bbtb.

Right now I'm actually thinking about building an ITB set up as a winter project, not because the car needs it per se, but because it'll look sweet*, it'll sound sweet**, and the throttle response will be sweet***



* might look sweet
** should sound sweet
*** could be sweet
lol

[tinkerputzer]

Fyi m50 throttle plate is 64.2 mm vs m20 60 mm if your planning to make your own bbtb.

[nando]

it's our firewall

yeah, you can defintely extend that powerband a bit with the 284/272. experiment with cam timing on the dyno to find the most power without sacrificing too much area under your torque curve.

a heat shield will make a difference on the dyno, but a much smaller one on the street (at speed, anyway). it's usually only when you're going slow or at a stop that the intake actually heatsoaks.

[Bullet Ride]

nice torque curve and power #s! it look's like you've done your homework - the cam timing probably helped you too, a lot of people skip that altogether.

what cam is it? I looked through the thread but the pics are blocked and I didn't see it listed anywhere.

you could probably break 200whp pretty easily by just adjusting your cam, it looks like it's biased towards torque, but on the street you may not want to do that. if it's a 284/272 or a 288 I'd have expected power to start dropping off at 6500 or later which would definitely get you there.

a BBTB might help but you should measure manifold pressure at WOT and see if you have any pressure drop before spending the money - and make sure if you do buy one, that they actually made it with a larger throttle plate (I got one that was supposed to be a BBTB, but it's really dremeled out and still has the stock plate). Also if you still have the stock airbox a large surface area cone filter will make a significant difference; I make less power than you and the stock airbox is a definite restriction.

Pics are blocked? I can see them fine. Does anyone else have problems seeing the pics? The cam is a schrick 284/272. When I get around to doing some dyno tuning I do plan on playing with the cam timing. I agree, I do need to observe my MAP reading at WOT to see where things are at, I was just speculating that since it's still stock it might be spot for improvement. My current intake is a 3" tube with a K&N cone filter on it, I still need to make a heat shield for it though.

"you could probably break 200whp pretty easily" ... That's what I like to hear :D

[nando]

nice torque curve and power #s! it look's like you've done your homework - the cam timing probably helped you too, a lot of people skip that altogether.

what cam is it? I looked through the thread but the pics are blocked and I didn't see it listed anywhere.

you could probably break 200whp pretty easily by just adjusting your cam, it looks like it's biased towards torque, but on the street you may not want to do that. if it's a 284/272 or a 288 I'd have expected power to start dropping off at 6500 or later which would definitely get you there.

a BBTB might help but you should measure manifold pressure at WOT and see if you have any pressure drop before spending the money - and make sure if you do buy one, that they actually made it with a larger throttle plate (I got one that was supposed to be a BBTB, but it's really dremeled out and still has the stock plate). Also if you still have the stock airbox a large surface area cone filter will make a significant difference; I make less power than you and the stock airbox is a definite restriction.

[Bullet Ride]

You should get the same answer within a few %. What wheels and tires are you running, was it in 4th gear and 3.73?

It was close, the number I came up with to multiply each mph value by was 54.35, using 5252 @ 92mph I got 57.1 about a 5% difference.