anti lag valve?

[IhmeJanneFIN]

22 hours ago, Reinhoud said:

Isn't your plenum too small?

It was originally about 3 litres if I can remember correctly, but it has been modified multiple times after that, so current volume is unknown. But it is much bigger in size than ie. Gsxr or Blandits that I have seen. I tried to mimic the oem gsx 750 f airbox in size and shape.

Edited August 18, 2023 by IhmeJanneFIN
damn typos

[Reinhoud]

On 8/18/2023 at 4:05 AM, IhmeJanneFIN said:

It was originally about 3 litres if I can remember correctly, but it has been modified multiple times after that, so current volume is unknown. But it is much bigger in size than ie. Gsxr or Blandits that I have seen. I tried to mimic the oem gsx 750 f airbox in size and shape.

My GS needed 2 x the displacement, I had to redo my plenum twice. It just didn't want to run properly, with the first one it hardly wanted to run at all..

[gorbys]

Antilag on the streets? I'm thinking you'd be better off getting a properly sized turbo. Antilag eats turbine wheels, can crack manifolds and exhaust pipes and ruin exhaust valves for example. My Datsun has been off the streets for two years now with a broken engine. Was the ten seconds of pops and bangs and no-lift-shifting worth that? Probably not. 

Anyways, there's a second option I didn't see here for anti lag and that's an electronic throttlebody. With that you can keep the throttlebody open on decel and retard timing and add fuel to make everything go bang in the exhaust. Don't know how easy it is to fit an etb on a bike though 

[TLRS]

The things that spring to mind.. A turbo that has low inertia (spools up quicker) and low resistance (keeps it revs longer). Small volumes to pressurize the turbo and the intake faster. A cam(timing) that increases engine output to start the turbo earlier. Which might cause the cam to 'run out' maybe at revs. But if the turbo can compensate for that..?

There are lots of interesting modern car engines. And usually it is no problem to find pictures. They can provide insight into what works as well. Like cars with V engines and 1 or 2 turbo's right on top, very close to the inlet. And cylinder heads that function as a collector. With the turbo bolted to straight to the head.

A reed valve to bypass inlet drag of the turbo is also really cool. Would it work with fuel injection though? Basically it creates a second air inlet. Depends on what sensors the FI relies maybe?

[Arttu]

Haven't personally tried antilag on any engine yet. But I don't think I would like to use it on streets. Like mentioned it's pretty hard on all exhaust side parts and quite noisy too.

There are few different ways to implement the antilag function. Without electronic throttle an external fresh air valve and plumbing is needed to feed air to exhaust manifold. Simultaneously extra fuel is added through the injectors and ignition timing is retarded. With electronic throttle the external air isn't needed but the throttle is just kept open during engine braking. Apparently electronic throttle approach is more effective and offers better adjustability for power delivery. In any case pretty good engine management and tuning is needed for proper functionality and good drivability.

[Arttu]

3 hours ago, TLRS said:

A reed valve to bypass inlet drag of the turbo is also really cool. Would it work with fuel injection though? Basically it creates a second air inlet. Depends on what sensors the FI relies maybe?

No problem with typical aftermarket EFI systems. A mass air flow based system could be a problem but these are very rare on bikes.

I guess that benefits of a priority breather valve depends a lot on turbo sizing and boost piping length. I have thought about trying it but when analyzing my data logs it seems that there isn't much need for it. Intake air pressure goes very close to ambient pressure right away when opening the throttle. So logically thinking the priority valve can't improve the resonse much. Maybe with smaller turbo which restricts air flow more it could be helpful.

[latheboy]

If you don't run a bov, wouldn't it be similar to an anti lag once you are up and moving?

I did it for shits and giggles one day and the bike pulled harder than a 14yr old when smashing through the gears.. it wasn't really happy about it  though and I didn't want to break it.

I recently took off the link pipe and fire it up. Blocked the pipe and it kept running just fine. 

Blocked the bov dump pipe and it stalled.. 

So mine it already potentially "breathing" through the bov at idle. 

I do remember from the old site people fitting bov's as a priority value on their plenums, I might add a second bov but only for the breathing action.. 

What could go wrong I hear you ask haha 

If I do a breather, I'll do before and after Dyno runs to compare.. 

Edited September 13, 2023 by latheboy
Speeeeeelllllling

[Gixer1460]

4 hours ago, latheboy said:

its already potentially "breathing" through the bov at idle. 

As it should be - any vacuum present should be sufficient to open the valve - which means any time pre boost.

[latheboy]

8 hours ago, Gixer1460 said:

As it should be - any vacuum present should be sufficient to open the valve - which means any time pre boost.

Yes, now that I'm sober I'm thunking betterer. 

If one works two will be better.

I have a 2" inlet and the bov is only 7/8", so it'll be a restriction.

[Gixer1460]

Not really - its only really open at idle and low speed and the whole inlet from air filter through turbo to plenum will be at atmospheric pressure once valve has opened - plenty air for normal NA operation. Plus its unfiltered air so not good in dirty climates !

[peter1127]

yeah I gave up on it. Good points all around: its hardly worth the trouble and might be unpredictable, pita to get right and even when its right it eats turbo's.  Just doing what always works: as large engine capacity as possible, dont lower CR too much and get tuning perfect in off boost situations. 

But the reed valve idea I like, I also saw this in the "show us your plenum" thread. So decided to add that. Found something of a KTM SX2016 including air intake that ofcourse also will have a filter. Also made a chamber that should even things out.