How to spool turbo sooner?

[Alex B]

Hello fellows,

Just as the question states what strategies in mapping can help spool the turbo sooner using only engine management system controlled parameters i.e. fueling, ign, injection timing, VVT (both IN and EX), DBW?

Any real life examples are welcomed as well.

Thank you for the input.

Alex

[Holmz]

Hello fellows,

Just as the question states what strategies in mapping can help spool the turbo sooner using only engine management system controlled parameters i.e. fueling, ign, injection timing, VVT (both IN and EX), DBW?

Any real life examples are welcomed as well.

Thank you for the input.

Alex

Alex,
You mentioned:
"i.e."
1 fueling
2 ign,
3 injection timing,
4 VVT (both IN and EX),
5 DBW?

How does "ign" differ from "ign timing"?


Firstly I have no experience with this, When I did a turbo install it was all home grown, with no ECUs, and just a carb... So I have zero real-life examples, All I can offer is theory...

You want both the exhaust volume and EGT as high as possible to get the maximum amount of energy into the exhaust, which in turn (pun) spools the turbo.
I have labeled the following by your topic #

1) At a fixed speed the F:A ratio influences EGT. I think that the curve has high EGT both rich and lean of lowest EGT (which it would have to have from the lowest point of EGT), and I recall, or imagine, that the lowest EGT is not far away from the best BSFC.
Bottom line is to adjust F:A to give a higher EGT. (But try not to destroy the engine)

4)The EGT is also influenced by cam opening position. Let us assume no spark... The higher the compression the higher the temperature in the air above it when it is at the top. At the bottom of the stroke the temp back to where it started.
Bottom line here is to advance the exhaust cam to get more energy into the exhaust and less out the crank, by opening the exhaust cam earlier.

5) To increase the volume, you need a WOT. On a race car this could work... But you would be giving up a lot of energy (fuel).

3) You can also retard the spark which would get less energy out the crank. As it must be going somewhere, I would suspect that it would be going into the exhaust.

That is one in every category you mentioned that I understand. I would not think that the intake cam would matter a whole lot at low RPM... I would probably bet on "advance it" - by have no idea.


I was doing this - I would want to understand the steady-state performance, and then select a strategy for returning to the boost condition separately. For instance for autocross/gymkhana you would not want to give up a lot of your forward motion in favor of turbo spooling. For a track car it might be possible to have the power linear with the throttle position, so that mid turn you are spooling.
In practice this can be difficult as the steady state tuning ignors the dynamic nature of the engine, and at some point you want to switch from putting energy into the exhaust to putting energy into the crank... Knowing the steady state performance would likely help a lot here.

What sort of car and application is it for?
I even find the lag of some DBW n/a cars distressing.

Best of luck with it.

[elton]

Ign,
and injection timing not ignition timing...

i was told to retard the ignition timing to spool up quicker, haven't tried it..

[stevieturbo]

retarding the engine will reduce power, and make spool even worse.

[Holmz]

retarding the engine will reduce power, and make spool even worse.

I am assuming that "spool" refers just to the turbo RPM.

From an intellectual pint of view I would be interested to know if you have data or experience to show that(?) or if it is based upon intuition?

[stevieturbo]

I heve retarded the timing and it becomes very lethargic as you would expect. It does nothing to promote spool, or power.
Certainly not on any engine Ive ever tried anyway.

The less power it is making, the less ability it is going to have to spool any turbocharger. Theory, practice, obvious.

[Holmz]

Hard to measure turbo RPM - so I guess boost (MAP) would be the go.

Spool is (or should be) a direct function of EGT and volume of exhaust.
Power and exhaust volume are related - both in the sense of that fact that more RPM means air pumping cycles/minute, and volumetric efficiency and boost meaning torque during each cycle.
Power (torque) might be a function of spool, but spool is not a direct function of power - being related only in a convoluted way...
Opening the throttle creates some value of instant torque, and increases exhaust gas.
Exhaust generates spool.
Spool creates more torque and more exhaust gas. (and power)
So yes power increases and spool increases, but it is spool creating power, not the other way around.

I agree that in practice getting the engine to a higher RPM more quickly is a good strategy as it is pumping more air through it. So advance/retard would not be as effective as a down shift, and unless the car is very slow to accelerate retarding the ignition might be counter productive.

Measuring EGT might be useful - I would expect higher EGT to a direct correlation with spool.
So it would be interesting to see some dyno plots with torque and boost at fixed RPM with different degrees or advance/retard, along with EGT.
Trying to do this with a dyno that does not allow for holding the RPM fixed would make it very complex.
So probably go for a fixed RPM and start off with light throttle and mash-it and measure things... Then go to the next RPM and repeat.

There should be some write up, or study, or book, of this somewhere???

[Karel]

As written, just more exhaust gasses at higher temperature can spoolup faster. Just let me ask: Do you need rotate turbocharger or make some power ? If you use it as an engine for a car, you schould try to achieve the maximum torq at every point at every boost and every throttle position. Some tuner are too lazy to tune partial throttle and are just tuning the max boost area. My idea is set the lowest boost as possible - tune it for the best result and climb higher and higher with the boost.
My experience is that too rich mixture kills spoolup. So try to be not too rich during spool up. Even stock EVO9 unit has an feature named "lean spool" to help.

Happy boosting

[Scott@FP]

With a Motec Mxx ECU is is very EASY (and inexpensive) to measure turbo shaft RPM, a $250.00 sensor kit, an open digital input, and some machine work on the compressor cover.

Also from our testing and experience airflow has an orders of magnitude higher effect on boost threshold than heat, the heat component of a turbine's 'efficiency' is a small percentage of the total. If you have a VVT system get that intake centerline in the 80's during spool areas.

[Aurélien]

retarding the engine will reduce power, and make spool even worse.

No.

It will reduce power , that's true , because you geat away from MBT. BUT you increase EGT and so you make turbospool better.

How do you think antilag works ?