Found some info on D2 while browsing around for some info on some öhlins struts. Its an interesting read..some good, some bad.
Quote: Also here is a copy and paste of his review of the D2 dampers when he took them apart. I was not kidding when I said this guy has his hands on a lot of dampers, and he knows them in and out!
Quote:D2 racing struts for the MR2_ MK1 Up-date #1
I received the used set of 4 coil-over assemblies from MicaCeli.
With the intent of running them on the shock dyno.
And investigate if there is any possibility of re-valving (re-calibrating).
For a more suitable ride, targeting autocross and performance street driving.
And from the start there were a few challenges to over come.
Not a big deal this is quite normal in the shock Biz.
# 1 D2 racing deviated from the production MR2 strut tab offset.
So I need to make a new dyno fixture to run them.
#2 the corrosion that accumulated from normal street usage.
Has become a minor inconviance. As water had collected inside the drilled shaft.
And had completely locked-up one of the adjusters with rust.
Also the steel threaded main body also seems to corrode to the threaded on aluminum fixtures.
I would suggest the other owners of D2 (and similar struts). Do some corrosion prevention work. To keep there struts in fine working order.
I would not leave the adjuster hex keys in place. As this is where the water enters.
I would remove them and instill an easy to remove plug to seal the opening.
Also I would take the time to remove the threaded on hardware and lubricate with anti-seize. So in the future spring seats and clevis hardware will move freely.
The best bet would be to send them to a racing shock expert for service.
And while there an oil change will keep things on track. Please remember. A racing shock can be quite dangerous. If the untrained attempt to service them!!!
As far as the quality of the product, it is better than expected.
I grade racing shocks like this. Based on quality and value for your dollar.
Penske Racing #1 value, flexibility and ease of use – (made in the USA)
Ohlins #2 a bit pricy, Excellent fit and finish,
Bilstein #3 nice value for the price. And a nice conservative approach to racing.
Koni #4 good value for the price.
D2 is not main stream here in the USA. But if it was I would place it as comparable to Bilstein. This set uses good quality racing internal components (Better than the low tech street stuff found in some)
There a few flaws but at this price I would call it a good value.
And when tuned properly will be a great performer.
It is a true mono-tube race shock with a single (no check) needle and seat adjuster.
Meaning the single adjuster changes both the Compression and Rebound low speed forces.
It is a true high pressure gas shock with an inline separating piston. Dividing the gas charge and the hydraulic shock oil.
Like I said, D2 Racing struts have a few design flaws. But at this price, is a nice value.
But do not forget. Just like any racing shock will require service to stay in top condition.
Next time I post I will supply dyno data from the as built struts.
And a bit of insight about a re-valve direction
Well I have disassembled one of the struts.
And found a few surprises. The working piston is an Ohlins copy (knock-off)
It is 42 mm & I have no knowledge of a 42mm Ohlins ever being used.
The aluminum parts from D2 Racing are quite soft and easy to damage.
And after a brief conversation with the salesman @ D2, they have little in the way of spare parts. No one is servicing them in the USA. And do not wish to repair or service the struts here in the states as they feel they are so inexpensive. It would be easier to just buy new parts.
The good news:
I have sources lined up for most of the seals. And re-valve parts.
And there should be no problem tuning this unit.
I also see the limited support from D2 racing as an opportunity.
Time will tell, but I feel we will be able to make this low buck monotube in to a winner.
D2 racing struts for the MR2_ MK1 Review _Up-date #2
Just the facts:
D2 Spring rates as delivered –
Front rate is 225 #/inch
Rear rate is 360 #/inch
D2 Spring package is a standard race size - 2.5 in. I.D. x 7 in. free length Front and Rear.
Stock Aw11 spring rates I have measured in the past-
Front is 85 #/inch (first inch, don’t have the installed preload length)
Rear is 178 #/ inch (first inch, don’t have the installed preload length)
AW16 Rear spring rate is 183#/inch
D2 strut total shaft travel is 4.75 in. stroke length.
But a droop spacer inside could be removed to increase that slightly.
The struts system friction is higher than I like. And is not consistent in the 4 units.
This friction is measured as seal friction on the shock dyno. But I feel it is not the shaft seal that is the largest contributor of the friction.
We have a plan to reduce this force.
The adjusters on the D2 struts tested have no effect on the damping forces. Twisting the knobs in all positions (full hard to full soft) showed no change on the shock dyno.
Sadly there appears to be a slight design problem that keeps the adjuster from actually working. I feel this can be easily corrected. And will up-date when it is fixed.
As you will see in the as delivered dyno curves they are as we thought.
Very stiff in rebound.
The right to left forces differ more than I prefer or are miss-built.
Will let you know more as we start the actual re-valve process.
Did a bit more work Saturday, and will be back at tonight.
Found a few items of interest.
#1 - A portion of the high system friction. Is caused by the clamped on sway bar tabs. They are actually distorting the strut body tube. Actually causing the working piston. As well as the separating piston to stick in the housing.
This is a big deal that needs to be addressed.
I was able to change the force curves on the dyno by simply tighten the pinch bolts.
We will need a new or modified sway bar link bracket. On the strut to correct this problem. (I was unable to tighten the pinch bolts enough to keep the clamp from spinning)(without impacting the struts performance).
But once corrected - this will add consistence. And increase the life of the unit.
Called D2 Racing NA this afternoon. And they now have a revised larger version of the Sway-Bar clamp bracket (currently out of stock). But it still uses a pinch bolt to lock it in place.
I am sure we can modify the clamps we have as well.
Item # 2
Work to make the adjuster functional, looks quite promising.
Will post adjuster force curves when I am become happy with the results.
P.S.
I was posting the same thing on honda-tech when I experienced the same results as him when I use to sell D2 and Ksport through the other company I owned which does retail sales. I too have taken apart and rebuilt quite a number of dampers myself. Selling them prior to me taking them apart gave me direct feedback from my customers. The D2's valving was crap, there corrosion resistant was horrible, and the adjuster didn't do jack shit. They only became decent after I reworked them, but after you add up the cost which was 150 a damper to fix, and the cost of the damper themselves you could have had something way better off the bat. Anything can be made to be decent, but some more than others. Trust me, I don't belong in the same sentence as D2, Ksport, and whatever..that's simply the truth. Funny, even after telling customers to stay away from those brands after taking them apart and finding the design flaws they continued to buy and support this crap. It's like they thought I musta been smoking something. They continue to fail, and make mediocre dampers. Now even if they did improve it they still stuck it to people because they sold something that didn't even work for years!! I completely stopped offering them through my other company when the calls of them blowing became such as hassle that selling them wasn't even worth it anymore.
