<p>I've been doing wastgate&nbsp;bypass testing at work lately to solve an overboost issue on one of our kits that uses a similar turbo to the china t25 turbos.&nbsp;</p><p>If you look at just the wired open versions you can see how adding the channel and WG port diameter size reduced the boost creep pressure. I don't have it on the table since it wasn't done in the same dyno testing but the original 25mm WG opening and no chanels saw about 9psi in the open wastegate configuration and 12psi spike on the auto trans 2-3 shift.&nbsp;</p><p><img src="http://cimg6.ibsrv.net/gimg/www.miataturbo.net-vbulletin/391x272/80-captured_20dba18dd1bf041ed0e0696edfd3df3fc0de51e8. jpg" title="" /><br /><br />&nbsp;</p>

 

This time I increased the diameter some. It opens at 9psi with 12 half turns preload where it opened at 9psi with 10 half turns preload before so clearly there is more pressure on the flapper. However it didn't creep past 10.25psi today although it is hot as hell and my IAT was reading around 90 to 95 F. I will give it another shot after the temperature cools down a bit.



Gaped like a giant bunghole, actually there is still room for more.

 

Or perhaps 10 half turns preload is max for this actuator. I will up it to 14 half turns before I go out this evening.

 

<p></p><p>&nbsp;</p><p>what are you trying to accomplish here? Increase your boost set point? By preloading the wastegate&nbsp;spring with 14 half turns (7 full turns) you are taking out a decent amount of total travel potential of the actuator. The actuator rod is&nbsp;something like 28 threads per inch so with 7 turns of preload you lost 0.25&quot; of travel. From the bench testing I've done on garett t25 wastegates they travel about 0.65&quot; total. So you reduced your actuator travel by 39% and have potentially reduced its capability to bypass enough exhaust gas to control its target setpoint of boost. Some china knock off wastegate actuators only travel 0.45&quot; and if you have one of those you now only have 0.20&quot; of acturator travel range which is most likely insufficient.&nbsp;&nbsp;</p><p>I'd suggestion something lower like 2-3 turns of preload and a boost gain type device or EBC instead.&nbsp;</p>

 

OK I will get a solenoid.

 

<p></p><p>&nbsp;</p><p>Or get an appropriately wastegate.&nbsp;</p><p>&nbsp;</p><p>but if you have a megasquirt the solenoid gives you many benefits and is well worth the $40ish price</p><p>&nbsp;</p><p>&nbsp;</p>

 

OK here is my log with the new port and wastegate wired open 8.4psi max. Any recommendations for a solenoid?

 

What gear is this? Reason being just because you ran it to redline doesn't mean it still doesn't want to creep. It looks like it still want to. Set you preload to 3 turns and run the log again. You want to find the top of the boost curve where it plateaus. You could easily put this car in 5th to do a full pull and creep beyond where you are now.

 

I see your point, this was 3rd. I am going to play with a bike pump on the actuator a bit to see what the travel looks like at different preloads and pressures. I will most likely get a solenoid from Trackspeed, looks like a nice little set for $60.

 

Plot from a pull yesterday. I haven't gotten to hooking up EBC yet and it's on a quality MBC for now. And VD plot of back to back runs on the same stretch of road to even things out.

My spark table is pretty conservative (still trying to learn this) so I'm sure there's more there.

 

add spark advance to that log.

 

What are you actually looking to see?

 

Check.

 

What the limits of this actuator are, even with 8 full turns preload it can still open the wastegate fully. The flapper arm only moves about 1/4", the total travel of the actuator is about 5/8". More than 5 full turns preload doesn't seem to do much, opens at 9psi with 5,6 or 7 full turns. Yes, it is the actuator that came on my kit.
I would like to run 12 psi from as early as possible to 6500. I suppose I could just get a 12# actuator but I will give ebc a try.
I can't seem to creep past 11psi, but 4th at 6000 is a bit faster than I like to drive. I think there are drag races tomorrow but I'm not sure if I can make it.

 

I don't understand the preoccupation with preload on the actuator. It needs to be tight enough to seat the puck. Then adjust targets with an EBC. The built-in adjustability in the aftermarket actuators is to set overall length and not to alter boost pressure. It will only do it in a very limited fashion, and poorly.

 

I agree, preload should be JUST tight enough that it requires you to pull the actuator out slightly to fit over the wastegate pin.

if you want to run more boost than your wastegate is designed for, use a boost controller.

 

<p></p><p>Your current 8psi ish wastegate and an EBC is the way to go. You can hold the wastegate shut until the last second and build boost fastly quicker than switching to a 12psi wastegate with no EBC. Also with an EBC you can set your pressure to anything from wastegate setting to #ALLOFIT with the Megasquirt software. Creeping to your target boost pressure is a function of poor wastegate bypass. A turbo setup that is set to 9 psi and creeps to 12 will respond poorly compared to one than hits the 12 psi target right away and holds it to redline.&nbsp;</p><p>http://www.diyautotune.com/catalog/e...kit-p-285.html</p><p>&nbsp;</p><p>&nbsp;</p><p>Exactly. Based on the spring rate of a 6.1 psi garrett each turn of preload will add about 0.3 psi to the actuator set point. The 8 psi garret is something closer to 0.4 psi per turn and is based on spring rate, diaphram effective area and pitch of the actuator thread. But this is a band aid solution to increase your boost pressure because you are reducing your actuator travel.&nbsp;</p><p>&nbsp;</p>

 

I just wanted to see, I am ordering a solenoid today and will post some more logs soon.

 

So another couple of pulls after working on the ignition map a bit. No other changes other then ambient air temp was cooler.




Faint lines are log overlay from previous pull on 7/20




Pulls are in order 7/20 - 2 runs and 7/22 - 2 runs pretty much on the same section of highway. Each set was back/forth.

I suspect the higher ending boost is result of the lower air temp and maybe the real reason for the higher HP numbers?

 

yes you will make more boost when it's cold. maybe 1-2psi