Read this in this book...
http://www.motolit.com/butuhielfuin.html

Here is a quote from the book ...

"Tuning an engine with forced induction on a dyno can be a daunting task. Trying to tune an engine that will lots of boost and a tone power can be even more challenging. These engines tend to make so much power when they come on to the boost they often will rip right through the RPM ranges you ar erying to tune. This can be very frustrating for a novice tuner.

One thing you can do to help out is to disconnect the turbes that lead from the turbocharger to the intake mniofld. This will prevent any boost from reaching the engine, so that you can tune it as you would a nautally aspirated engine. Just operate the dyno so that it will hold you at a constant engine speed while you adjust the load with movement of the throttle and tune all the sites as best you can.

Once you have tuned all the sites for wot in a naturally aspirated form, you can connect the boost tubes again and begin tuning the boost sites. If you have an adjustable wastegate or boost regulator, turn it down as low as it will go and tune the lower boost sites first and gradually work your way up.

When done properly, the shape of the fuel curve under boost should closely match that of teh engine while NA . It will simply use more fuel, resulting in higher numbers in the map. The reason for this is the because the engines volumetric efficeiency for any given engine speed is determined by the combination of cylinder head, camshaft, displacemnt, and should simply move up or down relative to the amount of boost."

Sounds cool...but what would keep the turbo from over speeding?

James

 

It allows you to concentrate on the NA portions of the fuel curve, and it makes it easier to tune into boost, cause you basically ignore all the vacuum ranges.
I've done it a couple times, and it makes for a nicer running engine on the street, cause of all the concentration on the vacuum ranges.


-Ted

 

I tuned my car NA first and then put the turbo on.

In my case it didn't make turbo tuning any easier.

Part of that is the 2ndary injector staging is the area I had to spend the most time on and it was only w/ turbo/boost. Another thing is even the idle was different w/ the turbo on it smoothing it out. It required less throttle pump setting in high rpm w/ turbo (I guess the heat of compressed air helped atomise fuel?) and liked more in the lower rpms for response (manifold burn). Even vacuum at cruise was lower so had to fiddle more for lean cruise.

Basically my engine was very different w/ the small responsive turbo on it.

The only way I found to do the top end of the map for a high power turbo besides the dyno is start pig rich and data log 4th and 5th gear high speed runs where you actually have enough traction to load the engine.

Not only do 1-3rd gear go by so fast only a data log can capture, but you don't have traction. It would be a pity to put slicks on and blow your engine just because it is now seeing a higher load than what was mapped since it has traction...

 

That is not how I would tune it... With the turbo and piping and ic not in place it would change the volumetric efficiency of the engine even at vacume load points and your map could be off when you hook it back up....

 

That and you are killing your poor turbo if you just leave the turbo on the car and disconnect its piping as advised in the 1st post....

 

not so much my man...more air in = more air out.

turbo pushes more air in to get more spool...if you can't boost, you exhaust coming out is limited.

A turbo can kill any engine.

Any engine can not kill a turbo.

 

What he is saying is that there will be no boost refrence to the wastegate because there would be no pressure in the piping. This would cause the gate not to open and the turbo would see super mega rpm's ending it's life rather quickly.

 

Why not leave it all connected and just take the spring out of the wastegate, should run at a few PSI tops.
Grant

 

Why not leave it all connected and just take the spring out of the wastegate, should run at a few PSI tops.

Definitely! Start w/ a low boost spring (you want similar boost response as final set-up) and map it up to that for the VE curve. Then interpolate and add a safety factor for higher boost and better compressor efficiency and go to the higher boost spring.

If you are patient

 

Totally agree ... unless you had a turbo tach Now that would be intersting!

Don't believe everything you read

But asside from that one blurb in that book I referenced...

It is a great book! He gives the unbiased run down on about 11 EMSs. It was some great reading to prime me for my first Haltech install.

James

 

If you guys tune on a steady state dyno none of the above should even matter... Unless the car makes enough power the burn them in 5th gear...

Taking the wastegate spring out will increase exhaust flow again changing the VE of the engine and again making your map not as close as it could be....

 

the motor will never build enough boost to open a wastegate regardless...it takes boost to build a "good" amount of boost.

yes, the turbo will be blowing into atmosphere, and it will be a lot of air, but I do not think this will harm any quality turbo.

MORE AIR IN = MORE AIR OUT
LESS AIR IN (no turbo) = LESS AIR OUT

what is so hard to understand?

 

Ok I see what you are saying now and it makes sence but wouldn't it depend on the size of the turbo? Im pretty sure a 2g eclipse would spool the **** out of its little t25 without the piping hooked up...

 

I would think that running the enigne at full power and the wastegate closed and never going to open. Would easily overspeed the turbo. There would be NOTHING to stop the turbo from spinning until it could spin no more.

James

 

Why not put a friggin plumbing/drain cap on the turbo compressor outlet so it is still "loaded" per se and won't overspin itself, yet none of the air goes into the engine? The exhaust will also respond just as it normally would when otherwise driving the turbo, because it is "loaded" and not freespinning.

I agree that a vacuum map formed without a turbo differs from one with a turbo. For instance, take a stock turbo 2 or FD with stock ecu (tuned for turbo) and plug off the turbo as described above to prevent damage, take it for a hard drive. Not only will be be weaker, but it'll load up and stutter in the midrange because it's far too rich for a given throttle position. THe ecu map which was formed for the turbo expects air to be pushed in (even when not in boost) rather than sucked in.

 

except the lack of exhaust gas it takes to spin the damn thing.

 

Hummmm good point

 

Everything in the system from your intake filter to your muffler have an effect on VE, so when you are tuning a VE table (base fuel table) wouldn't you want all of the components in the system to be hooked up! When I am tuning I dont even set the boost lower than what it will run fully tuned because the open wastegate has an effect on VE at the lower load levels...

Justin
www.alienauto.com

 

Yes I agree! with out any real loading there is not a strong exhaust pulse,so turbo is quite safe.
I road tuned my car this way.
once the basic fuel map is calibrated... just plug the plumbing back up and the map sensor should compensate for most of the maping on boost.


this is what is being done here in NewZealand by some tuners now. But i thought it was suposed to be a trade secret to some dyno tuners.