Haldex Fuse
There
has been a long running debate on whether its safe to pull the haldex fuse to
run your car on the rollers.
Tuners say its safe, Haldex doesn't think so.
A while ago I had questions and answer sessions with an Engineering and Quality
Manager at Haldex
The dialog is below for you to make your own conclusions, Personally I wont take
the risk, but read on.
Mats Johansson
Engineering & Quality manager
HALDEX TRACTION AB
44708 Helm Street
Plymouth, MI 48170
U.S.A.
PHONE +1 734 737 0435
DIRECT +1 734 737 0433
FAX +1 734 737 0436
CELL +1 248 910 9489
E-MAIL mats.johansson@haldex.com
name: Waheed Khan
question: Hi, I have a technical Question that is causing a lot of debate and
discomfort amongst many enthusiasts and would appreciate it if you could give
me a definitive and technical answer to help me propagate the information.
I hope you will appreciate that the Haldex units are being used by many
enthusiasts like myself ( www.wak-tt.com ).
Some of us get our cars power tested on rolling roads and myself I will only
run on a 4wd drive rolling road, others pull the haldex fuse and run power
runs up to 130mph with the rear wheels stationary.
The Question is I believe that this could be harmful to the haldex others say
there is no harm.
Can you confirm or deny what you believe, I'd appreciate a technical
explanation if possible. If you think it should be ok or its bad I'd just like
to be able to confirm to the other owners.
your help in clearing this up would be most appreciated. regards Waheed
car: Audi TT
submit: Send
Hi Waheed,
Yes, we definately appreciate all the enthusiasts out there with the Haldex
coupling :)
You are also right regarding your question. To pull the Haldex fuse to remove
the AWD function is fine when it comes to lower speeds but the speeds that you
are talking about is definately not good for the system since the driveshaft
will not stop spinning just because they are removing the fuse. Removing the
fuse makes it easier on the Haldex coupling but at high speed it is still
getting some beating.
Best Regards,
Mats Johansson
thanks for the quick response, can you offer any more details.
Most appreciate its a wet clutch system with 2 sets of plates that are pushed together the problem is the debate around this is if the fuse is pulled, the plates are seperated, the actuators are disabled , so what is the concern about damage?Is it not the case that there is simply a drive shaft spinning with not torque being transferred to the rear within the box?
The other question related to this is your website FAQ states that 2 wheel towing is allowed but see your manufacturer for recommendations.Is there a maximum speed or duration of towing that Haldex recommend for safety?
many thanks for your time, sorry if I am asking for more technical details but these enthusiasts are highly technical.Plus I am also interested in the engineering side of it. :o)
best regardsWaheed
Well, the concern is that unless they remove the drive shaft there will still be rotation sent in to the coupling.The discs (7 of them, not 2) is separated but with the high rotation of the driveshaft the pistons inside the coupling will start pumping the oil around in an open loop in the coupling and in high speeds there will be a slight pressure (drag torque) that will cause the discs to press together. If you are only using one set of rollers that means that the coupling tries to transfer torque to the rear wheels that are strapped down and not moving and the coupling, driveshaft and ptu get more loads then they are ment for. (got a bit confusing there, just get back to me if you do not understand what i mean.)
When it comes to two wheel towing i can unfortunately not answer you regarding the limits. We (haldex) manage very high speed for a very long distance but there is more parts then Haldex on the powertrain so we have to follow the vehicle manufacturers recommendations.
_________________________________________
Mats Johansson
Engineering & Quality manager
"To ensure the function and minimum activation time, the annular pistons are constantly in contact with the rollers via a low pressure, maintained by a small electric pump in the coupling. The pump works only when the vehicle's engine is running. The coupling is deactivated when the engine is off, making it possible to tow the vehicle with one axle lifted. "
Doesnt this mean that the pump wont be running when the fuse is pulled?Waheed
Best Regards,
Mats
As I understand it, when driven on rollers the input shaft is turning and the mechanical pump activated because of the difference in rotation between input and output. This input shaft rotation is where the problem occurs in the hi speeds achieved against a stationary output shaft.
When Towing, front wheels are off the ground, the input shaft is stationary and the output would be turning because the rear wheels are being turned. But the pump is driven by the input shaft so is not running and this is ok for the short duration and low speed during towing.Does that sound about right?
:o)best regards
Waheed
_________________________________________
Mats Johansson
Engineering & Quality manager
HALDEX TRACTION AB
44708 Helm Street
Plymouth, MI 48170
U.S.A.
PHONE +1 734 737 0435
DIRECT +1 734 737 0433
FAX +1 734 737 0436
CELL +1 248 910 9489
E-MAIL mats.johansson@haldex.com
"This e-mail is confidential and may contain legally privileged
information.It is intended only for the addressees. If you have received
this e-mail in error, kindly notify us immediately by telephone or e-mail
and delete the message from your system.
E-mail is susceptible to data corruption, interception, unauthorised
amendment, tampering and viruses, and we only send and receive e-mails on
the basis that we are not liable for any such corruption, interception,
amendment, tampering or viruses or any consequences thereof."