Dinan Supercharger - Why so much higher M3/Z3M vs 328/Z3?

[peakay]

Hey there,

Can anyone explain why the HP/Torque gain is SO much higher on the M3/Z3M vs 328/Z3 on these old Dinan kits?

Dinan sent me a doc (from July 1998 - see attached) with all the old parts and specs and I didn't expect them to be the same, but the results on the 328/Z3 are so much lower than on the M3. M3/Z3M gains 104hp/81tq vs 50hp/49tq for the Z3/328

Did they up the boost or pulley on the M3/Z3M kit? Anyone know why this is?

Just wondering if any of that can be applied to the 328/Z3. My understanding was the SC kits were largely the same hardware-wise and the motors are pretty similar.

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[circuit.heart]

I don't recall if the blower and pulley are the same, but all else being equal, the stock M52 cams are awful at high end and you can see exactly where they choke. If you used the S52 cams you'd likely see another 20-25hp, which would percentage-wise put the gains around the same area as the S52's supercharger gains.

[peakay]

I don't recall if the blower and pulley are the same, but all else being equal, the stock M52 cams are awful at high end and you can see exactly where they choke. If you used the S52 cams you'd likely see another 20-25hp, which would percentage-wise put the gains around the same area as the S52's supercharger gains.

Thank you very much. That could very well be... my gut is its something else. The torque curve from the Z3M falls off a ton after 4k rpm the same as the Z3, yet the torque curve with the SC just on Z3M continues upward in a much smoother way as if boost is coming on earlier.

What intake manifold does the 98 Z3M have? Same as standard Z3 or is it the M50? Does it have ASC+T?

[pbonsalb]

Centrifugal boost increases as a square root of rpm so torque should stay pretty level whereas normally it drops after naturally aspirated torque peak in the midrange. The OP has an ins Powerdyne. We don’t know what Dinan Z3M it is being compared to. Maybe a Vortech system? Maybe a rare higher powered intercooled model (Dinan made a few but I forget the application). Maybe the S54 version of the Z3M?

[Colby Colbs]

Different engines basically. I believe this is comparing a 2.8 to a 3.2L engine. Different cams, different rev limit, and perhaps different intake manifolds. Exhaust systems play a big role on these setups as well. The m3 stuff is all around better than the 328 stuff out of the box. That is the big difference. The M3 will move more air period.

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Slightly different compression ratios as well! The 328 coming in at around 10.2-1 VS the M3 @ 10.5-1.

[peakay]

Different engines basically. I believe this is comparing a 2.8 to a 3.2L engine. Different cams, different rev limit, and perhaps different intake manifolds. Exhaust systems play a big role on these setups as well. The m3 stuff is all around better than the 328 stuff out of the box. That is the big difference. The M3 will move more air period.

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Slightly different compression ratios as well! The 328 coming in at around 10.2-1 VS the M3 @ 10.5-1.

Thanks, I hear ya, but same basic kit on an expanded/enhanced version of the same engine and double the HP at the same RPMs? Both cars with Dinan exhaust. Seems a little off.

[pbonsalb]

328 is 15% less displacement than M3. That affects torque and horsepower, all other things being equal. But all other things are not equal. The M3 cams are better and that helps upper rpm power. As the 328 cams are falling off, the exponentially rising centrifugal boost curve offsets the loss, but that offset is multiplied on the M3 due to the better cams.

Look at where the 2 motors are in N/A form. 189 hp for 2.8L vs 240 hp for 3.2L. 2.8 goes from 189 to 253 or about 34% and 3.2L goes from 240 hp to 338 hp or 40%. Not much difference in % at all but what is there is probably due to the cams.

[peakay]

@pbonsalb thanks for the figures - yeah, not too far off. 41.6% gain for the M3, 34% for the 2.8. I’m less concerned about that than the difference in the curves. M3 just builds torque and Hp in a pretty continuous fashion, the 2.8 has 2 different power bands with a bridge between them.

I guess the question is how would I make the 2.8 more like the M3 in terms of curve? What is really causing the difference? A modest bump in boost would probably be the easiest to shift power/torque to the left, but if there’s a way to uncork the engine and get results I’d rather do that.

I have an M50 manifold I could take install, but do not want to let go of the lower end torque for a higher peak number way up in the stratosphere RPM wise. Thinking of trying an ASC delete and test the changes.

[pbonsalb]

M50 manifold adds top end power but sacrifices low end. The bigger 3.2L handles the loss better, and some mods like shorty headers, tune and Schrick cams were dyno tested to minimize that loss on the 3.2 years ago.

Of course the M50 was used on the 2.5L M50 so if you don’t mind rowing the gears to access power then it is a good choice. I suspect BMW turned to the smaller runner manifold for emissions purposes. Bumping boost by 2psi would help but is risky with a powerdyne and your kit probably does not have a bypass valve. Can’t go more that 2 psi because there is no intercooler. It is not easy to add one though it has been done.

A shorter diff wakes the car up. 328 has a 2.93. When I had a powerdyne, then Vortech S then Vortech T on my M3, I changed from the stock 3.23 to a 3.38 from an auto M3 to a built 3.64. The 3.64 made me want a 6 speed and that is when I changed to a turbo and to a 3.15 diff — the turbo makes so much more torque than the centrifugal.

Having been all the way down the centrifugal road, I would skip it and go turbo.

[peakay]

Thanks again for the informative reply @pbonsalb . I’m not on a massive power quest with this car, but thought those comparative curves were odd (the 2.8 drives exactly as the curve suggests) and it would be nice to make it them more similar.

Regarding upping boost, I don’t have a boost guage on the car, so are you familiar with how the boost builds on these? My assumption is it builds to a peak at max hp, but not sure if that’s correct. With regard to upping boost, I don’t find myself winding it to the rev limiter much, so if I ran an 8lb pulley I’m thinking it would shift the curve left and not much of a risk unless maxing out the rpm’s. Is this thinking correct? Or does boost max out earlier somehow?

Oh, also, what intake mani does a 98 Z3M have?

[pbonsalb]

Centrifugals increase boost exponentially. Basically, you get peak boost only at peak rpm and you get the square root if peak boost at half peak rpm. So if you get 7 psi at 7000 rpm, you get 2.7 psi at 3500 rpm. You may feel a really modest increase in power from 3000-4500 but the fun is 4500-7000.

If higher rpm is not your driving style, a centrifugal is not a good choice for you. It is a dumb idea to run a small pulley to try to make it produce more low to midrange boost because you will be short shifting. 8 psi is not that much more than the stick 6-7 psi. You still won’t make 3 psi at 3500 rpm. For anything over 6-7 psi, the powerdyne needs a bypass valve and I don’t think the Dinan kit includes one since it is intended to be low boost.

98 Z3M has the M52/S52 small runner OBD2 intake.

[peakay]

Centrifugals increase boost exponentially. Basically, you get peak boost only at peak rpm and you get the square root if peak boost at half peak rpm. So if you get 7 psi at 7000 rpm, you get 2.7 psi at 3500 rpm. You may feel a really modest increase in power from 3000-4500 but the fun is 4500-7000.

If higher rpm is not your driving style, a centrifugal is not a good choice for you. It is a dumb idea to run a small pulley to try to make it produce more low to midrange boost because you will be short shifting. 8 psi is not that much more than the stick 6-7 psi. You still won’t make 3 psi at 3500 rpm. For anything over 6-7 psi, the powerdyne needs a bypass valve and I don’t think the Dinan kit includes one since it is intended to be low boost.

98 Z3M has the M52/S52 small runner OBD2 intake.

OK, thanks - that's how I assumed they worked, but wanted to verify. I do like high RPM driving, but just don't run into the rev limiter much and am not looking for a torque monster. Just wondering how to improve that torque curve so its more like the S52 with a continuous build and not a flat area in the middle, plus closer to the overall amount.

Given that an S52 is an M52 with bigger bore/stroke and better cams, I'm wondering if Cams are the most important factor? The displacement is only 15% bigger, yet the torque peak with the SC is a full 100 lbs more. Are cams easyish to swap on these and are S52 cams easy to pickup?

On the need for a bypass valve, why is that? I assumed the biggest risk would be if spinning the blower above its max rpm, but I wouldn't think a small boost increase pulley would do that.

Thanks for all the great info.

[pbonsalb]

Cams are not hard to swap if you are patient and careful. Best to have someone who has done it before help you, especially with the vanos timing. Cams are the most important factor for upper midrange and top end. Bypass valve relieves pressure when you lift off or shift and the throttle closes. Otherwise the boost backs up into the supercharger. With the fragile powerdyne internal belt drive, you can blow the belt.

You are trying hard to pound a square peg into a round hole. A centrifugal will not make an M52 into a torque monster, S52 cams won't make an M52 into an S52, and a smaller pulley won't do much for low to midrange boost. A centrifugal is not a good choice for you and a powerdyne is the worst choice among centrifugals.

Maybe do an S52 conversion instead. Or even an S54 conversion. Or turbo the M52.

A shorter diff will multiply the torque you have better. After going through the Powerdyne, Vortech S Trim and then T Trim, I dropped compression slightly with a 0.098 MLS and ran the smallest pulley that would not slip and that was with an 8 rib 6.0" crank pulley and got peak boost of 16 psi. I made about 4 psi just before 4000 rpm. I went from a 3.23 to 3.38 to 3.64 diff trying to multiply torque -- that helped but highway rpm went up. With the turbo, I went to a 3.15 diff for much more relaxed highway driving. I made 16 psi by 4000 rpm. My torque was about 50% higher.

[circuit.heart]

Honestly, at the power levels you're asking for, you don't need forced induction. A stock S52 with ITBs, intake and exhaust can make almost as much power as the Dinan supercharged S52 with none of the complexity, heat, or weight. I don't think you're ready for the care and feeding of aftermarket forced induction either - it's never as painless/brainless as companies want you to think.

S52 cam swap + M50 intake manifold on an M52B28 will wake it up plenty, no torque loss but the peak continues growing almost all the way to redline. I enjoyed driving this combo even more than my S52 as the 2.8L is smoother and happily revs to ~7500.

[Colby Colbs]

Thanks, I hear ya, but same basic kit on an expanded/enhanced version of the same engine and double the HP at the same RPMs? Both cars with Dinan exhaust. Seems a little off.

Two completely different air pumps! It's all in the details and proof is in the pudding a they say!!

[peakay]

Cams are not hard to swap if you are patient and careful. Best to have someone who has done it before help you, especially with the vanos timing. Cams are the most important factor for upper midrange and top end. Bypass valve relieves pressure when you lift off or shift and the throttle closes. Otherwise the boost backs up into the supercharger. With the fragile powerdyne internal belt drive, you can blow the belt.

You are trying hard to pound a square peg into a round hole. A centrifugal will not make an M52 into a torque monster, S52 cams won't make an M52 into an S52, and a smaller pulley won't do much for low to midrange boost. A centrifugal is not a good choice for you and a powerdyne is the worst choice among centrifugals.

Nope, not trying to make it a roots blower. Have had two of those (Miata and Hellcat) and am familiar with them. Great info on the bypass valve, I did not know about those, but have been looking into them now. Just learning here.

Two completely different air pumps! It's all in the details and proof is in the pudding a they say!!

If they were two completely different motors I would never have asked have the question. We're talking two variants of the same motor, but I understand one is significantly enhanced

Honestly, at the power levels you're asking for, you don't need forced induction. A stock S52 with ITBs, intake and exhaust can make almost as much power as the Dinan supercharged S52 with none of the complexity, heat, or weight. I don't think you're ready for the care and feeding of aftermarket forced induction either - it's never as painless/brainless as companies want you to think.

Yes, that's a great point, but the car came with the system, so trying to learn as much as I can. Plus its CA smog legal and unique, which is kinda cool.

I just went through the whole system, having the head unit rebuilt, repainted the brackets, new hardware, belts, hoses and all new cooling system. I'm doing a backroads rally with it this weekend and will see how she does. Thanks all for the great info.

[Colby Colbs]

Different valvetrain, different crank & stroke, bore size, compression, different exhaust systems, they are not the same motors. While they share some architecture, they are two completely different animals, designed for two completely different purposes. Believe it.

[BimmerBreaker]

If the M52 and S52 are "different engines" then an M54B30 and M54B25 are also different engines 🤷🏻

It's not like we are talking about an S50 vs M50 or S54 vs M54

[pbonsalb]

To me, the biggest differences are displacement and cams, which together account for the roughly 25% power differences. In the subcategory of displacement, the pistons and crank differ. M52 also has a lower compression ratio.

I think the percentage increases with the respective Dinan kits are as expected given the engine differences, but the OP either disagrees or does not understand the engine differences and how centrifugals work.

[peakay]

OK, after rebuilding the SC and installing a new cooling system I got the chance to drive the car in a backroads rally. Honestly, the 2.8 with the Dinan SC is great for that and I wasn't wanting for power or torque anywhere. The early torque ramp and flat build up thereafter works really well for this kind of driving, so not really wanting for any major power differences.

The only thing I might do is install an ASC delete elbow and try to incorporate a bypass valve to help cooling and longevity.

Thanks for all the helpful info - I definitely learned a few things.

[pbonsalb]

Before you buy the elbow look into the bypass valve. There are elbows with 2 nipples instead of just the one for the IAC valve. The 2nd nipple could be for a bypass valve, but you will still need to add the return port to your supercharger intake pipe between the HFM and blower inlet. Some kind of bulkhead style fitting might be best for this unless your pipe is metal, in which case you could weld a nipple. The little Bosch plastic bypass valve with 1” inlet/outlet should be fine. I like the diaphragm style valves like that for this low volume use.