Homebrew studderbox

[Vlad Busta]

Anybody know how the studderbox exactly works?  I'm thinking of starting up a homebrew studder box project.  I remember reading somewhere that to get the car to stay at one RPM you retard the timing that the ECU sees.  

Don't know how easy it would be but I was thinking that the module would need inputs from the car's speed sensor, throttle position and tap into the cam sensor some how.

Am I on the right track or what?  I know alot of you guys would enjoy a low buck studderbox  

I think I'll hookup the datalogger to confirm that the timing does infact get retarded when using the studderbox then I could look into ways of duplicating the desired timing value.

I guess it could also be used as a saftey feature when you drop your car off to get serviced, keeping the RPMs below 4000 lets say.

Just thinking about it.  Any info or opinions welcome.

Later, Vlad.

[Andrew Steele]

hahahaha yeah ... droppin the car off at Satan for whatever reason, set the rev limit to like 3K ... and tell them "there's monitoring equipment in the car, so don't f*ck with it. I'll find out if you do!"

[Jeremy Clarke]

Yeah that would be a sweet valet feature

[Vlad Busta]

Yah that valet feature would be sweet but not as sweet as launching the car at 5500 RPM with 10 psi of boost  :twisted:

Later, Vlad.

[Kevin Standeven]

what prevents the boost from building when your car is revving but sitting still, is the wastegate open? and how does the wastegate (or whatever else prevents it from spooling) differentiate between revving in neutral and revving in gear? or am I overlooking something here...

[JamieSibley]

While revving in neutral, the engine isn't accutly under much load. Idling at 800 rpm and revving to 5K in neutral both use less fuel and air than crusing down the street off turbo. When a stutter box is used, it cuts spark to certain cylinders in order causing misfires. The rapid missfiring simulated a load on the motor and causes the turbo to spool.

A simple stutter box design would be to have the signal to 1/2 (cly. 1,4) of the power transistor cut off when the engine hit's x rpm.  Not a true stutter box, but should hold the revs pretty close to where you want them.

In a real stutter box (msd dis-2) for example, the higher the engine rev's past the set rpm point, more and more sparks are taken away from the plugs.   set at 5000 rpm, it is almost impossible to get it to rev past 5500.

[Kimyee Lai]

The factory rev limiter actually cuts fuel, but for a home brew it might be easier to cut spark.  Retarding the timing COULD possibly be used, but it won't be easy to implement timing control on the ECU w/o something like a TMO chip.  I know when I retard timing to -15, the RPMS rise quite slowly.

[Mike Schmid]

Yeah, Jamie pretty much nailed it.  It's a question of load... the engine isn't under enough load in a free rev situation to spool the turbo decently because it's only working against internal friction.  The waste gate will be closed or close to it when just free revving because the turbo isn't getting enough exhaust pressure to spool at any appreciable boost level.  You'll also notice that to hold a 5500 rpm "idle" free revving takes very little throttle, hence, low load, hence, low exhaust output.  That's where auto's are nice, you can brake torque and use the brakes as a load, with slippage being taken up in the torque convertor.  

With a stutterbox you cut spark so you can run WOT at 5500rpm, additionally some stutter box setups will only cut spakr, not fuel, so the extra fuel will be at least partially combusting in the exhaust manifold and creating a larger than normal pressure differential across the turbine.  Severely retarding the timing will also result in fuel combusting later than usual, meaning: in the exhaust manifold, that's how the anti-lag setups on WRC cars work AFAIK.

[John Hartman]

sounds like fun Vlad, but if you are going to make em cheap, you are gonna have to make em real cheap.  You can get a stage 2 chip from whatshisface for $75 US.  And its more than a stutterbox

I say go for it tho, I love this sorta stuff.

[Tim Hunt]

You can get the vehicle to build boost at rest with no load but you have to find a way to advance the timing at that point, this is how DSMLink V2 performs it with it's antilag feature, not good for the engine though, 5 secs and you are doing perminant damage, but for 1 sec at the track it's fun, an AWD launching at full boost is a well, violent situation to say the least.