OS-88 Gear Shift Control

[iecku.tavea racing]

Has anyone done it with a Link Ecu?

Hope you could give me some informations to do it right :-)

[Scott]

Hi,

Is this the transmission you are talking about?

http://osgiken.net/c-1280291-transmission-os-88-sequential-transmission.html

The page doesn't give much detail on the sensors. Hopefully the transmission comes with a strain gauge lever and a rotary gear position sensor. If it has these then the Link G4+ Gear Shift Control will be capable of working with the transmission.

Scott.

[iecku.tavea racing]

We measured the electronic box which comes with the os88 gearbox. It only gives signal for the led gear indicator, neutral and reverse. :-(

So we have to go with a shift knob with microswitches or strain gauge.

[Scott]

The micro-switches or strain gauge can be used for telling the ECU when the start the gear shift control, but the ECU also needs some way to know when to finish the cut. One option is to use time and then the ECU will do the cut for the time specified. A nicer solution is if the gearbox has a sensor that is able to say which gear is currently selected. Does the LED gear indicator have an LED for each gear? If yes, does it use one wire to control this or a wire for each gear?

Scott

[iecku.tavea racing]

Hey Scott

We are doing it with a shift knob with microswitches. The electronic which comes with the OS-88 does not provide anything you could need.

We´ve found an remote cable throttle blipper from pro-shift. Do you think we could use it with the G4+ extreme. The current it takes is 16 amps!!!

[Adamw]

I suggest that you fit a proper gear position sensor (barrel position).  I have tried the spring loaded switch type gear levers many years ago and they dont work very well. I built about three versions before giving up.  If you had a gear pos sensor then you can control the gear cut from that without any microswitch knob or strain gauge.  A poorly setup gear cut system will wear out the drive dogs in a matter of hours so it is in your interest to do it properly. 

As for the blipper - you cant drive a 16A load directly but with a relay it will be good.  Since you need quite fast response and its a big inductive load I would suggest using a solid state relay.  I have had good success with the small Hella 4RA 007 865-031, as a bonus they plug straight in to a normal automotive relay socket.

[iecku.tavea racing]

@adamw: thanks a lot for you suggestion! *thumbs-up*

[Steve]

The ssr dont use the same pinout tho. Even though they do fit in a regular relay holder. Make sure you understand how to wire it or you will ruin it...

[mapper]

Hi Simon

In general is a strain gauge needed or suggested if you have a potentiometer on the sequential gearbox? Or can we just use the the position signal to start and end cut? 

 

 

[Adamw]

Hi Simon

In general is a strain gauge needed or suggested if you have a potentiometer on the sequential gearbox? Or can we just use the the position signal to start and end cut? 

 

 

Hi Mapper,

I have some experience with both methods.  Strain gauge based cut initiation gives the absolute best result but obviously comes with a price tag.  Barrel position cut initiation actually still works pretty reasonable but you need a longer, more noticeable cut event and the actual shift is slower.  I guess this more prominent shift cut event may also have traction consequences to consider in some disciplines.

The difference is with a strain gauge your cut doesn't initiate until a preset shift force is reached - this preloading removes all mechanical backlash from the gear linkage/barrel/shift forks etc so the gears are basically ready to "pounce" as soon as the torque reduction is activated.  With a barrel position based system you initiate the cut basically as soon as movement of the barrel is detected so you are already cutting power when you still have all the backlash to "use up" and the gears havent even thought about starting to move yet...

[mapper]

Hi Adam 

Thank you for the answer. Wery helpfull.

Can't the position sensor adjusted that it cuts only if you pull some amount at the lever, so that it only cuts when some force is pulling the lever back? 

What shift times you see whith both methodes? 

[Adamw]

Hi Adam 

Thank you for the answer. Wery helpfull.

Can't the position sensor adjusted that it cuts only if you pull some amount at the lever, so that it only cuts when some force is pulling the lever back? 

What shift times you see whith both methodes? 

A picture will probably explain better:

This picture is not scaled well to what I normally see in real life but it still shows you the idea.  The green arrow is pointing to roughly where I would normally initiate the gear cut based on system using gear lever force.  The red arrow shows where I would have to initiate the cut if we where using barrel position.  You will notice the gear pos volts is a "flat line" in the preload area so we cant get the cut to trigger in the ideal location.

As for your "shift times" question, unfortunately there is probably not a typical answer - you will see huge differences between cars, vehicle weight, gearbox type, etc.  All I can say is I only have one example of similar cars I have played with using the two methods, if I were to take a guess based on feeling and incomplete data I would say the total shift time is about 25% longer on the car that uses barrel positon.