Pre-spool Valve for Launching

[Edub1]

Check this out. Just a half baked idea but it just might work. Tell me what you think.

The idea is to use an electric valve that will act like a BOV, only it will stay open and vent any pressure as long as the clutch is depressed.

The lack of pressure should allow the turbo to spool up pre-launch and if placed before the throttle body will set up an air flow in the IC pipe.

So, you can rev the motor and have the turbo spin up under 0 load. Then when you release the clutch the valve springs closed and your already spinning turbo makes instanat boost.

[lilskyline240]

from what i know, a turbo only produces boost when there is stress on the engine....and with the engine reving in nuetral there is virtually no stress...

for your idea, your goin to vent excess pressure?? wouldnt that be like a giant vacuum leak?? and wouldnt ur car stall??

[KATwo40]

Yeah, this would also be another way to re-invent the 2-step system.

A properly sized turbocharger won't spool up this way without the timing retard required to keep the exhaust gas at a high enough velocity, while not loading the engine.

Also, if it would work, you'd need a speed density system, so you wouldn't stumble from the chaotic MAF information.

[Edub1]

Re-route the air so it returns between MAF & turbo.

The turbo should spool with a few good revs and the motor held at 4K for a launch. Again, it will have no pressure working against it untill the valve shuts. There might even be energy in the circulating air mass to boot.

[C-Kwik]

What's more important is putting the load on the engine to get enough exhaust gas flow. Even with such a bypass, the turbo wouldn't be spinning anymore than it would without it since the engine would be taking in and spitting out the same amount of air. Since the turbo swon't be seeing any more exhaust gas flow, it won't have anymore ability to spool quicker.

If youre clutch can handle a little extra heat and still grab, you can try putting a slight load onto the engine while holding the brake and letting out the clutch a bit just prior to launch. If you have an automatic holding the brake with a bit of gas just before launch can have the same effect. Should allow you to get into boost just a hair quicker.

An even better pre-spool valve would be a NOS solenoid with it's corresponding equipment. Another trick is to actually try to mash the throttle a little before launch to try and spool the turbo slightly. It can be a little tricky to maintain consistency while timing the light well, but some practice can probably help.

[Edub1]

You don't think that stomping the peddal a few times and holding 4000 RPM will get the turbo spinning in a situation where there is no resistance in the compressor side? What about stomping again as the clutch is released?

Normally there would be intake pressure working against the compressor wheel. Stomping the gas, against the load of the resting motor does produce a large exhaust quantity and should spin up a turbo. The problem is, it creates boost (pressure) which stops it again. vent the resistance and it should spin a little better.

I'm not suggesting that the turbo would be running full tilt, just that it might help get a little of its mass in motion a second or even a fraction of a second faster.

Supposing you are correct about the turbo not spinning, then the valve would work in reverse and allow air to bypass the resting compressor allong a less obstructed path. That's gotta be good.

[180sx]

get a varieble geometry turbo!

[KATwo40]

Ehhh...here's an idea...

You remember that your stock ECU has a secondary map for 5th gear? What if you used a launch control map with extremely retarded timing and low rev limit (4500rpm) to achieve some WOT launch control (also known as 2 step)? You would have to configure a toggle system that's actuated via switch on the clutch pedal to switch between maps.

NOTE: Can't use the 5th gear switch, because I tried this for just a generic launch control and intermittently experienced non-recovery from the kill function. I would dump the clutch, and the engine would fall to zero until I hit the clutch pedal again (to click the switch) to make it recover.

DeviousKA was working on some alghorithm analysis to find out what causes this malfunction, but he's pretty busy and hasn't completed that project yet. He will when he gets time, I'm sure.

[deviousKA]

Is that what it was doing? It wouldnt recover from the 5th "state"? I kind of forgot the symptoms you ran across.

It should have, and extremely quickly (.001 sec maximum). Maybe the switch was hanging?

I have realized now with a little more research and discussion that the 5th operation is quite basic and not associated with speed or a more complex algorithm as I had assumed before. The 5th limiter is rpm related only, and this location has now been found by Calum for the sr20de and ka24de. With a clutch pedal switch to ground, wired into the 5th gear wire, the rev limit can be set to whatever you would like and you would have a complete fuel table dedicated to this launch state. Unfortunately it would be quite difficult to have a seperate timing table dedicated to launch with the ka24de, but maybe not with the ka24e.

This is not the best way to accomplish a launch limiter (unless you desire the same limits and fuel maps during shifting [flatshift]), but it would work ok.

Maybe inspect that switch and try it out again. The limiter should be ~4950 rpm. The oem fuel map that would be running at the same time is plenty safe, just a tad rich.

[deviousKA]

eh,

Found the quirk, Ill try fathom a workaround.

The rpm must drop below the limit while the switch is engaged before it will disengage. If the switch is disengaged before rpm drops the ecu sticks with the limit untill you push the switch again at a lower rpm.

[thekawaii]

from what i know, a turbo only produces boost when there is stress on the engine....

SO TRUE!

[C-Kwik]

You don't think that stomping the peddal a few times and holding 4000 RPM will get the turbo spinning in a situation where there is no resistance in the compressor side? What about stomping again as the clutch is released?

Normally there would be intake pressure working against the compressor wheel. Stomping the gas, against the load of the resting motor does produce a large exhaust quantity and should spin up a turbo. The problem is, it creates boost (pressure) which stops it again. vent the resistance and it should spin a little better.

I'm not suggesting that the turbo would be running full tilt, just that it might help get a little of its mass in motion a second or even a fraction of a second faster.

Supposing you are correct about the turbo not spinning, then the valve would work in reverse and allow air to bypass the resting compressor allong a less obstructed path. That's gotta be good.

Mashing the throttle a few times would technically be no more helpful than doing it once. But it does tend to help in getting a rythym and range down prior to launch.

Using a bypass to allow air around the turbo for less resistance is a valid concept. Many factory BOV's and some aftermarket ones have this capability.

[edubb11]

What you want is an anti-lag setup. Here is a description:

http://www.rallycars.com/Cars/bangbang.html

[KATwo40]

eh,

Found the quirk, Ill try fathom a workaround.

The rpm must drop below the limit while the switch is engaged before it will disengage. If the switch is disengaged before rpm drops the ecu sticks with the limit untill you push the switch again at a lower rpm.

That's exactly the problem I had. While launching was fine with the setup, it would fail between shifts. I run it up to 6500rpm and quick shift, then it would fall on it's nose, defeating my psuedo-flatshift feature.

Let me know if you find a workaround. Perhaps raising the 5th gear rev rebound would do it, but that would require finding the location. I'd love to get this setup working correctly as a lauch/flatshift control.

[deviousKA]

I commented on your post over at FA, no one over there is going to know wtf you are talking about.

You can accomplish exactly what you want at this point, but it requires hardware. You can switch the rev limiter and fuel/ignition mapping at will.

What is your current setup and what are the specs of your planned turbo setup? If you wanted to do something with this, let me know and maybe we can work something out. You have a soldering iron?

The last few boards I have here before the next batch comes in are going to be dedicated to various enthusiast testing, I am willing to offer the components at near cost but only for interesting projects.



External launch limit/flatshift connector (also can be used for hi/low boost tune switching) shown.

[KATwo40]

Yeah, you're right, Devious. If it doesn't include "SR20DET" in the post, they just shrug it off.

My currentt setup is stock KADE with the T3/T04E, 370's, Walbro255, SAFC2, runnin' 8psi on a 195k mile engine.

However, I have a build in the works and it's nearly complete. I should have it in the car and runnin' by the end of this month.

Fully built bottom end, balanced and blueprinted, .020" overbore, 12.5lb flywheel, full engine stud kit.

Head is ported, 248/248 cams, stock valvetrain.

T3/T04E .50 trim (.60 A/R housing.), T-31 .76 trim turbine wheel (.63 A/R housing)

FMIC (31x6x2.75)

Walbro 255 (prolly gonna have to go twins on that for my power goals)

740cc/min squirters

Z32 MAF

Plannin' on running 12-15psi on the street, 20psi on the track (400-425whp/tq)

I'd love to volunteer my project as a guinea pig for your products.

[deviousKA]

First of all let me say this.

Your never going to see me selling $400+ generic ka-t ecu's like everyone else. The way I see it, the only necessary product that this market REALLY needs, is the physical hardware that is required for them to take care of the tuning themselves.

A "tuned" ecu is nothing more than a fully controllable system sitting there with a single set of adjustments.

In the real world of standalone tuning, files are traded basically freely. Why? Because those using them are usually experienced with tuning, and know that they are bascially going to have to go through the entire tune anyways (as always) to do it properly, no matter how similar the engine. All engine setups are different, different components in different conditions. You can build two identical engines and then go grab yourself two sets of identical used engine parts (injectors, maf, ecu, coil, wiring), put them up on a dyno with a pro tuner for more than a couple hours, and they will be fine tuned differently.

Things people wouldnt even think about with used parts like wiring resistance variables due to difference in connections, differences in electronic pcb component condition, battery charge injector latency compensation etc etc..

I guess you could say i take it a little too seriously, but thats why I dont tune mail-order, I dont feel right doing it. Any information I have I usually just give away for free unless I spend extra time handling it, and sell some hardware just so people have a place to get it. My boards are only 35 dollars, shipped

Just incase any mods think im just out to sell parts

KATwo40, feel like trying with your current setup next week? Ill send you an email.

[KATwo40]

I'll check my email tomorrow (Sunday). I will be throwin' some dirt on the new dirtbike in the morning, so it will be afternoon or evening.

Yes, I want to do this next week. I can start playing with the setup with my current configuration, which will give me some familiarity with it before I slap the new mill in later this month.

Thanks again.