M5x and S5x over M20.. Why?

[nando]

Dynos can be reasonably accurate if the tuner/operator isn't messing with the correction factors. Using SAE on a dynojet I got ~218whp on my 330i which is pretty reasonable for 255bhp. Of course you can make the number whatever you like by using a different factor (or none at all), but that's why there are standards like SAE (or Shootout-6 on a dyno dynamics).

[SkiFree]

I got 4 E30s two with M52 swaps and two with M20. Everything is better with M52B28, they are very cheap now, get better gas mileage, better power band, better throttle response, smoother idle, better resale value.

I get to drive around in a 6-speed swapped S52 and an ITB'd 3.1L M20 e30. The M20 engine delivers so much more character it's not even close. It loves to r3v and has a much more period feel. Smiles per/mile the M20 is the obvious choice.

As time goes on an M20-engine e30 will have a much higher value than an M52 e30. Yes, the M52 is a "newer" engine (despite the fact it's now nearly thrity years old), but if I wanted something newer and more efficient, I would have bought a newer and more efficient car. If I wanted something cheap, I would have bought a Honda. In short, your factors are less relevant by the day.

[digger]

Dyno numbers are relative, a fresh m52 with intake and cams should make about those numbers. A fresh m20 with the same crank, itb and mild cam coincidently makes about the same torque and hp.

[jeenyus]

And the valves tick twice as loud.

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[MrBurgundy]

And the valves tick twice as loud.

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A properly functioning head wont have any valve noise if adjusted within spec.

Everyone seems to forget out loud those injectors are.

My valve trains makes no noise when warmed up, but my injectors are loud as fuck

[jeenyus]

You're right. The injectors are loud and it's not just the m20 injectors. I replaced min with 4 pintle Bosch injectors and they are still loud.

A properly functioning head wont have any valve noise if adjusted within spec.

Everyone seems to forget out loud those injectors are.

My valve trains makes no noise when warmed up, but my injectors are loud as fuck

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[e30davie]

I pulled the engine cover off my brothers mazda 3 engine. And it made a huge difference to the injector/valve train noise. Maybe there is a market for engine covers for the m20....

[DBShiznit]

I get to drive around in a 6-speed swapped S52 and an ITB'd 3.1L M20 e30. The M20 engine delivers so much more character it's not even close. It loves to r3v and has a much more period feel. Smiles per/mile the M20 is the obvious choice.



As time goes on an M20-engine e30 will have a much higher value than an M52 e30. Yes, the M52 is a "newer" engine (despite the fact it's now nearly thrity years old), but if I wanted something newer and more efficient, I would have bought a newer and more efficient car. If I wanted something cheap, I would have bought a Honda. In short, your factors are less relevant by the day.

Glad I’m not the only one who thinks this way


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[AWDBOB]

It's nothing personal, just my impression based on the fact that most dynos are optimistic and 94hp/l (based on the 265bhp number you posted) from an M52 with cams and an intake manifold seems a little high. I'm highly skeptical of shop dynos, they have an incentive to inflate, as does the dyno manufacturer. When people see dyno numbers of a stock car and go OMG IT'S UNDERRATED FROM THE FACTORY!!! Most of the time I say no, dynos at tuning shops are usually optimistic, and the manufacturer would have no incentive at all to underrate, barring some sort of limit like the infamous 276hp japanese car. When more horsepower is always a good selling point, why underrate your engines? Car companies are trying to make money from a wide audience, not make inside jokes that "real" car guys will get, like "BMW underrates their engines!"

So, when I see that an M52B28 is rated at 190bhp, and I see a dyno which is showing numbers like 178whp for that engine (stock aside from the muffler), my first impression isn't that the driveline is incredibly efficient (~6% loss) or that the engine actually made over 200bhp from the factory instead of 190bhp, I'm thinking the dyno number is a little inflated. It's great for comparison to see the gains of the cars with the tunes, but the actual numbers are of less important than the shape of the curves and the gap between the lines.

That's why when I tune someone's car, I tell them that dyno numbers are more of a ballpark figure, and a dyno is only truly useful for comparisons such as before and after tune.

I agree in that dyno numbers are a ballpark, but I think accurate results can be achieved if you use the tool how it's designed. Mustang Dynos "read low" out of the box but can be heavily modified to suit whatever results are optimistic.

Dynojets are typically accurate from one dyno to another without adding a correction factor, as it's testing exactly what that car is making on that day at that time/temp/etc rather than adjusting for temp, pressure and humidity. SAE is nice for shops to compare (I think Market uses STD) so that way they can't say "oh well it was hot this day so that's why this car made less/more/whatever". Post-correction all cars are being 'tested' under the same calculated conditions, effectively.

Dynojets are nice, though, as there are much less susceptible to inflation due to standardized CFs.

I've seen smoothing inflate numbers as well. You could have a choppy, spikey curve that when "smoothed" excessively takes a couple spikes and magically gives you 10whp when you smash the graph down, when in reality your car isn't making that.

It is funny though- I've seen tuners post up a pre and post graph, and leave the initial run uncorrected on a hot humid day and then the post tune graph corrected to help them sell their services :D

Anyway, back to m20 stuff.

[digger]

the twin roller dynos are more inconsistent as they rely much more on the tie down procedure and tyre parameters/setup.
Correction factors get you only so far, if the ECU pulls timing because something is too hot then the correction doesn't account for that.

one of the traps people also fall into is using an engine that has mileage to come up with bogus drivetrain losses. the BMW m20b25 makes about 150-155 whp stock when fresh. its 168hp SAE when stock, so that's only circa 10% "losses" this doesn't mean the factory underrated it because they certainly didn't.

[nando]

yeah, lots of people will use 20-25% for drivetrain loss so they can imagine an inflated BHP #. No way, especially not on a modern car - maybe back in the 1960s they were that high, but those are low hanging fruits for engineers trying to claw every bit of fuel efficiency they can.

Plus on a 300whp car that would mean 100hp is turned into heat - and drivetrain losses aren't a straight % anyway..

[brian52555]

Why bother even turbo'ing it? The M20 is a very underrated engine and has proven time and time again to hold it's own. 230whp-245whp is now easily achievable while still having good road manners (and using 91octane).

However, I get that kids just want to do a "motor swap" because it's almost a right-of-passage for any gear head. To each their own, we are all friends here.

I've been away from the e30 scene a while... any details on how 230+whp is easily achievable on an M20?

Thx

[varg]

I guess it could be "easy" if your wallet is sufficiently full that you can just open it wide and have a high compression stroker with a worked head and ITBs built and put in your car. You won't be making that kind of power with any stock M20 parts spinning around in your block though without forced induction or nitrous, short of being some sort of magician.

If it were easy, everyone would be doing it.

[Vivek]

The funny thing is though, a basic M50 swap is hardly faster at all in reality than a decently running M20.

Steven was driving our b25 e39 wagon the other day (7 people in it, but anyways) and wondering why anyone would swap such a slow engine into an e30. There are minor improvements with extra valves and lifters but 90% of e30's would be better off with the same $/energy put into maintenance and suspension.

I'm planning an m62/6 speed for my 318...the slowest engine worth swapping in would be an s50 imo.

[agent]

the slowest engine worth swapping in is an OBD2 M52 or later

Maybe an S50 if it's a bargain.