ATI vs GDM harmonic damper, S5x engine

**aeronaut** · 05-29-2022, 07:56 AM

Are the GDM Engineering and VAC ATI damper one in the same?

I see some older threads about the harmonic damper from GDM Engineering.
I've seen some pics, and I swear the GDM looks like the VAC ATI.
GDM Engineering seems to only exist on facebook, which I don't.

**eacmen** · 05-29-2022, 10:01 PM

I’ve heard nothing but complaints from ppl running aftermarket harmonic dampers on the s54. Would avoid and stick with stock.

**pbonsalb** · 05-30-2022, 08:48 AM

The OP has an S52. I have been running the VAC unit for a few years without issue. Apparently it is smaller than one of the few other offerings for aftermarket dampers, but I don’t know how much that matters. Worth looking into. You don’t need any special tools to install the VAC but I have read that at least 1 of the others requires an install tool due to the extremely tight fit.

**aeronaut** · 05-30-2022, 08:51 AM

Yep, I should have been specific, I'm S52.

**ScotcH** · 05-30-2022, 10:25 AM

Never heard of the GDM. Been running the ATI for years on S52 and M54 ... but I've also been running a stock M54 with the AC pulley cut off, and that engine spins to 8000rpm all day (for 3 years now), so not sure if the ATI is really needed

**aeronaut** · 05-30-2022, 11:58 AM

I'm not compelled to spend $1k on a damper, was hoping there was an option other than VAC/ATI.
Maybe I'll buy a new OEM from FCPEuro, and replace as/if needed, or keep a spare used one close at hand.

harmonicdamper-failure.jpg

**ScotcH** · 05-30-2022, 09:25 PM

Ya it's brutally overpriced. You can find ones for LSx for like $200.

**pshooter** · 05-31-2022, 07:41 AM

Agreed on the overprice. That seems to be common in the BMW world.

However, think for a minute about that damper failure. The reduction of weight on the clutch end of the crank combined with sustained high rpm operation and inherent crank dynamics issues
only makes the dampers job harder. I see that many crank snouts with the stock damper on disassembly have been fretting for some time. The dual mass flywheel is an awesome torsional damper. A 16 lb clutch assembly not so much.

While the ATI or any other viscous damper is not the cure they do work as intended and our s/m5x engines need all the help they can get.

**aeronaut** · 05-31-2022, 07:59 AM

I'm not on facebook, so can only see a few pictures. Here's the GDM stuff.
https://www.facebook.com/pages/categ...6097734687654/

Oddly, the pictures I see say "ATI SuperDamper", and I can't find any current pricing.

**R.Thomas** · 05-31-2022, 08:26 AM

I suggest you talk to Perry (SomeGuy2800 here on BFC).

**pbonsalb** · 05-31-2022, 10:03 AM

The GDM version uses a larger ATI damper than VAC. I don’t think an AC pulley is possible and it is more involved to install - I think a special tool is required.

**aeronaut** · 05-31-2022, 10:13 AM

Ahhh... so it seems to be targeted to higher HP or RPM or such?

**ScotcH** · 05-31-2022, 11:08 AM

I f'ing hate FB businesses. How do I see any prices? How do I buy any of that crap?

**aeronaut** · 05-31-2022, 11:14 AM

Originally Posted by ScotcH

I f'ing hate FB businesses. How do I see any prices? How do I buy any of that crap?

Right? I don't get it. I tried to buy something from Massive a few years ago and it turned into 40 email exchanges trying to understand what was available and for how much. I gave up and swore off all FB-only buisnesses.

Thanks for reminding me.

**pbonsalb** · 05-31-2022, 11:37 AM

Originally Posted by aeronaut

Ahhh... so it seems to be targeted to higher HP or RPM or such?

Maybe bigger power? Some of the turbo guys use the bigger damper. I have only about 700 rwhp and use the VAC ATI, but I also never had any trouble with the stock damper on my S52 and don’t rev over 7200 or track the car. I installed the ATI only because I found one for $400 years ago and that seemed reasonable.

**aeronaut** · 05-31-2022, 01:06 PM

I'm at 7200 limit right now, and just use it to avoid a shift at a few places on track when I'm lazy. Power optimized shift is around 7000.

It seems there are no $500 aftermarket dampers, so for now I'm going the spare used OEM route.

**zemaestro** · 01-19-2023, 08:06 AM

We answer millions of questions on IG and Facebook…The damper has gone through multiple revisions, with a newer lighter hub being prototyped now…I have street units that are AC capable which use the 2jz shell. That particular unit overdrives by 25% and is RPM limited based on that fact alone…it’s a killer unit that Real Street has used up to 2000 hp, even though it exceeds its design limitations. My race unit was originally designed by ATI for Adam Hale. A particularly combative VAC employee made fun of the unit, and next thing you know their “Pro Extreme” damper was released…
The race unit can be had with 25% underdrive pulley and also supports a trigger wheel option. There are also two damper options…

**aeronaut** · 01-19-2023, 08:13 AM

Do you have something other than IG and Facebook for more detail?

**golgo13** · 01-19-2023, 02:25 PM

Originally Posted by zemaestro

We answer millions of questions on IG and Facebook…The damper has gone through multiple revisions, with a newer lighter hub being prototyped now…I have street units that are AC capable which use the 2jz shell. That particular unit overdrives by 25% and is RPM limited based on that fact alone…it’s a killer unit that Real Street has used up to 2000 hp, even though it exceeds its design limitations. My race unit was originally designed by ATI for Adam Hale. A particularly combative VAC employee made fun of the unit, and next thing you know their “Pro Extreme” damper was released…
The race unit can be had with 25% underdrive pulley and also supports a trigger wheel option. There are also two damper options…

This is interesting.

I'm S54 and have been looking into alternatives over OEM because that part is a consumable and is overpriced for a rubber disc.

I'm frustrated that VAC cornered the market with their 3x priced ATI unit, so I won't be buying into that monopoly.

I am however considering the unit from Ross so hearing that there might be another option here in the US gives me hope. I need it to support A/C for now though.

**aeronaut** · 01-19-2023, 04:37 PM

Originally Posted by golgo13

This is interesting.

I'm S54 and have been looking into alternatives over OEM because that part is a consumable and is overpriced for a rubber disc.

I'm frustrated that VAC cornered the market with their 3x priced ATI unit, so I won't be buying into that monopoly.

I am however considering the unit from Ross so hearing that there might be another option here in the US gives me hope. I need it to support A/C for now though.

Hmmm...I wonder if their M50 B25 damper would work on the US S50/S52 engines?
https://rossperformanceparts.com/pro...rmonic-damper/

- - - Updated - - -

And again, GDM doesn't seem to make any information available. Posting a response to a thread with your companies name in it, 7 months after the post is dead, telling users to ask questions via FB and IG, isn't compelling to me.

**ScotcH** · 01-19-2023, 06:05 PM

Originally Posted by aeronaut

Hmmm...I wonder if their M50 B25 damper would work on the US S50/S52 engines?
https://rossperformanceparts.com/pro...rmonic-damper/

- - - Updated - - -

And again, GDM doesn't seem to make any information available. Posting a response to a thread with your companies name in it, 7 months after the post is dead, telling users to ask questions via FB and IG, isn't compelling to me.

Interesting, 800 AUD, so decent price ... shipping might be annoying. I don't see why the M50 damper would not work. If you have S52 with rear crank trigger, I'd opt for the M54 damper.

(and yeah, agree on GDM ... must be marketed to a different crowd.)

**circuit.heart** · 01-19-2023, 06:46 PM

Originally Posted by ScotcH

Interesting, 800 AUD, so decent price ... shipping might be annoying. I don't see why the M50 damper would not work. If you have S52 with rear crank trigger, I'd opt for the M54 damper.

(and yeah, agree on GDM ... must be marketed to a different crowd.)

I don't know if that's safe to assume. If they actually tuned the damper for the B25 crank it would likely be effective for a much higher rpm than the "danger zone" 7000-7400 of the S52 crank. OTOH, who the heck is revving an M50B25 to 9k? So maybe it's just a generic 7000+ damper which would work for us.

**ScotcH** · 01-19-2023, 07:49 PM

Originally Posted by aeronaut

Hmmm...I wonder if their M50 B25 damper would work on the US S50/S52 engines?
https://rossperformanceparts.com/pro...rmonic-damper/

- - - Updated - - -

And again, GDM doesn't seem to make any information available. Posting a response to a thread with your companies name in it, 7 months after the post is dead, telling users to ask questions via FB and IG, isn't compelling to me.

Originally Posted by circuit.heart

I don't know if that's safe to assume. If they actually tuned the damper for the B25 crank it would likely be effective for a much higher rpm than the "danger zone" 7000-7400 of the S52 crank. OTOH, who the heck is revving an M50B25 to 9k? So maybe it's just a generic 7000+ damper which would work for us.

That's a good point! but I would venture that it's most certainly a generic damper.

**pshooter** · 01-20-2023, 07:21 AM

I run the ATI for years and recommend it for any S5x build that will see sustained high RPM.

I've seen many failed stock dampers.
If you've removed a stock damper and noticed that "rusty" spot on the crank snout. That's fretting. The damper twisting back and forth on the end of the crank.
The better fit of the ATI is a huge plus.

**zemaestro** · 01-20-2023, 05:35 PM

Originally Posted by aeronaut

Do you have something other than IG and Facebook for more detail?

I do not…what questions do you have? Pictures are generally very good at conveying information regarding the general layout of the damper design. Do you have IG or Facebook accounts? I make myself available to answer question as I am a believer in customer service. I can tell you that my damper and cylinder head will likely be on the most powerful turbo and NA engines in the country. This is a hobby, and myself with a few others are continuing to develop parts and push the envelope of this platform. It’s a selfless venture with no real payoff. Please don’t be so coarse. We are here to help.

coming this week… flanges that will adapt my CNC exhaust port to S54 headers. Regarding the head…We developed the cylinder head using the S54 as a benchmark. We outflow it top to bottom, intake and exhaust, with excellent airspeed. Dyno results straight from Kassel coming in March, it will be pass or fail. Either way I am excited to disprove 25 years of bad (often repeated) information surrounding this amazing platform.

Regards Travis Sarno