|
Post by mattturbocar on Jun 10, 2013 14:32:46 GMT
Hi there,
So I've megasquirted a gsxr1100 using gsxr600 throttle bodies and a td04-16T.
td04-16T has a internal dump valve and I have plumbed that into the map sensor AFTER the throttle bodies (the standard 4 into 1 MAP outlet).
When I datalog this, I close the throttle and I get a boost spike. But this is after the throttle bodies! Surely when I close the throttle the pressure is supposed to drop, open the dump valve, and then drop some more? Obviously I've done something a bit wrong.
I don't mind fitting an external dump valve, but at the moment if it is going to see pressure increases when I close the throttle, there isn't much point.
What have you chaps done?
Matt
|
|
|
Post by danm54 on Jun 10, 2013 14:47:54 GMT
Do you mean waste gate?
If you've got your take off after the TB's this would put a vacuum on the line to the waste gate holding it closed once you close the throttle off.
Id take it from the plenum so it'd be reading positive pressure when you close the throttle and it should then open.
I'm no expert though!
|
|
|
Post by mattturbocar on Jun 10, 2013 14:52:48 GMT
No not the wastegate. Agreed wastegate needs to go to high pressure (in my case to plenum, which is on the turbo side of the throttle plates).
Dumpvalve is for when the turbo is spinning fast, but throttle plates get closed. Without a dumpvalve the compressor on the turbo gets stopped by all the high pressure gas that it is trying to pump which knacks it, also massive pressures can damage the throttle plates.
Dumpvalve is normally actuated by vacuum. So close the throttle, vacuum at dumpvalve so it opens and you don't get massive pressure in inlet and turbo keeps spinning.
|
|
|
Post by danm54 on Jun 10, 2013 15:02:13 GMT
Ahh I see, assuming the spring is the right size and the dump valve isn't faulty then I have no idea.
|
|
|
Post by arttu on Jun 10, 2013 16:04:43 GMT
How big boost spikes you have on the datalogs? I'm having some 200-300kPa spikes every now and then when closing throttle. I have had these with my both turbo setups so I guess it's more or less normal. I think it's kind of false reading due to dynamics of the air flow. When you close the throttle the pressure in the plenum spikes before the BOV reacts and releases it. Since flow area on the throttle decreases the air speed past the throttle blade increases and pressure spike in the plenum amplifies this even more. I guess this may lead to momentary pressure spikes between the throttle and intake valve when the valve is closed. So even though effective average pressure past the throttle drops the MAP may read even higher pressure than what is in the plenum at the same moment. This is just my own theory. But I haven't noticed any ill effects due those pressure spikes. No bent throttle blades nor ruined compressor wheels
|
|
|
Post by mattturbocar on Jun 10, 2013 20:28:57 GMT
Wow Arttu your spikes dwarf mine. Here is a trace So my little spikes are nothing compared to yours, but either way I'd like to get rid of them. I was thinking of feeding the dumpvalve from the inlet boot on cylinder 3 (you know the one that normally is used as a vacuum take-off for the fuel line tap). Do you know if that has a more accurate pressure reference. Matt
|
|
|
Post by arttu on Jun 11, 2013 4:15:29 GMT
Wow Arttu your spikes dwarf mine. Oops, I meant 20-30kPa. And that's maximum, mostly the spikes are below 10kPa. So very similar to your graph here. I wouldn't be too worried about those spikes but of course it would be interesting to try to cure them. I have no idea if changing the take off port makes pressure signal more accurate. I doubt it but on the other hand that's easy to try. At least having a dedicated take off for the BOV may improve it's reaction time.
|
|
|
Post by mattturbocar on Jun 11, 2013 8:33:26 GMT
I'm pleased that you hadn't been ignoring 2-3atm spikes.
My guess is the same as yours, i.e. the throttle body reading is wrong in this situation, which is a limitation of these k1-3 gsxr TBI's. It doesn't matter much for the fueling (in my case I use TPS and MAP signals), but I will explore different takeoffs and if I see improvements will report back.
Like you say it isn't a big deal. But I'd like to get it right and then I can have a boost limit where I want it.
Thanks,
Matt
|
|