Low RPM chip timing for faster spoolup.

[KEVINS]

OK guy's,
What are the theories for making a turbo hit max boost AS FAST AS POSSIBLE from an idle?

I was power braking my car into boost while recording it on DS and it was 34* around 2500rpm with maybe 5psi of boost.

To me I would think that less timing would help the engine rev quicker because the spark plug isn't firing so early forcing the piston back down AND more of the exhaust "flame/heat" would be heading out the exhaust valve sooner which would spool the turbo quicker.

What are the ideas reagarding low rpm timing for doing this? Why do chips have so much timing down low?
Anybody experiment with the low timing?

Let's talk about this..
KS

 

[TWIN86GNS]

In the past I have run and run quickly with chips from Don Kiger (the old timers might know this name) and his chips had a LOT of timing, 36° from what I recall and they were always very responsive. You could not run as much boost on a chip like that but did they ever work, you needed GOOD traction to launch. Sorry my post wasn't very helpful, but it described what I have seen with my own cars.

 

[KEVINS]

Thanks Paul. Yea, I can understand the timing for the upper RPM's but I'm curious to what the timing was from 2000 up to 3500-4000 RPM or so and what the reasoning was.. Any idea?

ks

 

[larry33kc]

Good thread. Subscribed

 

[TurboBob]

Don Kiger's chips were bone stock for low RPM timing if I remember.

low timing makes less torque. Fuel does not burn instantly, and the timing advance is there so that the pressure peaks after TDC. But low timing makes more exhaust heat. So its a balancing act.

When brake torquing, if you reduce the timing, you get less torque, which will reduce your RPM since you can't push into the converter as hard. But it will increase exhaust heat. There is not one answer that fits all.

Generally on the street, more torque drives better.

Bob

 

[87GN_70GS]

Set the wastegate coeffiicient to "FF".

When I was playing around with this years ago, I reduced the timing at conditions where I would be power braking. I.E., rpms below stall speed, mid-level LV8, etc; I used logged data from some typical power brake situations that I felt I would likely be in. Then I increased the timing back above stall speed. Theory was this lower timing "spike" put more heat into the exhaust for a few seconds. And when rpms got above stall, timing kicked back in and made some torque.

I also pegged the boost at anything below the shift point drop-back rpm. Example, the rpm just after shifts was 3500, boost was set at max below 3500 rpm. Theory was the WG solenoid would be held open, boost would build as quickly as possible and that the engine would only spend a small amount of time overboosted as it came up through first. Due to lags, it never really built up way too high, just a few psi (sometimes 4 or 5) over what is was set to when hit the drop-back rpm, etc. It usually just blew the tires off anyway so there was never really any load on the engine during this overboost. 2nd through 4th boost was where it was set to be.

Don't know if this was the best set-up, but it seemed to spool up pretty good, and came up through 1st quickly.

 

[87GN_70GS]

But if you're going to just flat-foot it from a dead idle, I would say to not lower the timing.

 

[TurboBob]

yeah, there are lots of "boost building" strategies (my chips have "launch assist" that does stuff like this), and when brake-torquing, you are not moving so who cares what happens to the torque. But all of the strategies that make the car easier to stage and launch at the strip make it drive like cr@p.

Bob

 

[TurboTnZ06]

I've found the best way to spool fast is to keep the wastegate closed. I run a 15# spring in my external gate and open it manually with boost and an old school ATR bleeder valve. All else being the same and running a THDP style pipe with a factory style HD actuator and solenoid, it would spool too slow.

 

[TurboDave]

All else being the same and running a THDP style pipe with a factory style HD actuator and solenoid, it would spool too slow.

Is this a generalization or specific to your car? I ask this because there are ways to spool quickly the the THDP style and factory style HD actuator! Without messing around in the chip. But it does generally require an electronic boost controller to take control of the stock solenoid. Either open loop controller or a closed loop controller. They can be set up to keep the actuator closed during spool up.

 

[KEVINS]

I just wanted to keep this discussion pertaining to chip programming. I wanted to see what has been tested to accomplish the fastest spoolup through the programming in the chip.

ks

 

[TurboTnZ06]

I've had JayC add timing to my chips back when I moved from Dallas, Tx to where the DA's were 10,000 ft in the Mtns of Colorado. It was a quick bandaid rather than changing converter etc. When I moved back to FL where the DA's were normal, my spoolup increased such that it would knock from that spike in timing. Having been through that, I'd rather control spoolup through proper equipment rather than bandaid it with a chip upgrade that is sensitive to DA's and then only be able to adjust it with a chip is problematic versus being able to feed more or less air through a boost controller which is essentially a mechanical operation. I've run RJC and ATR manual boost controllers, electronic boost controllers, none of it worked perfectly on the THDP style setups for street and strip until I went to an external gate where I could adjust springs and feed it boost however I want to adjust the spoolup and have it open when I want for rock solid boost at WOT through the gears. My powerlogger says I go from 0 to 20+ psi in a half second or less now

 

[TurboBob]

I agree that the stock tension wastegates can open too easily, especially with a ported wastegate hole. In these cases, the checkball style boost adjusters can aid spooling.

in the chip, turning the solenoid on to 100% earlier than stock can help some as well.

The electronic boost controllers can aid spooling, as they use a solenoid that has more control over the wastegate signal, and can even help a stock tension actuator spool faster.

But, for boost response driving around, the keys are having a sensibly sized turbo for the application, and an appropriate torque converter to match. Then the tune needs to be right. Spooling takes 'mass flow', mass flow comes from HP, which comes from torque. Reduce any of these and spooling suffers. You can play games with reducing spark to spike the heat, but that reduces torque so you really don't gain anything.

So the best thing you can do for spooling is pick the right parts, after that, make sure the tune is on, then experiment. I did the same thing about 10 years ago, and found no magic wand.

Bob

 

[KEVINS]

I'm curious, if more timing adds torque but could increase detonation, could more timing be used and alchy injection used to eliminate the detonation?

KS

 

[ijames]

I'm curious, if more timing adds torque but could increase detonation, could more timing be used and alchy injection used to eliminate the detonation?

KS

Yes but a smidge too much alky kills the egt and you get no spool at all . It's a real tightrope.

 

[KEVINS]

Well, my recent purchases over the last two weeks include a PTC 2800 converter, Razors alchy injection, an audible knock detector and Erics TT chip set for high boost for this stock turbo. Now I need the time to get it all installed and some alchy and more time to tune, but once it's tuned it should be a pretty fun ride around town..

KS