So here's something I've been pondering, and I have a few ideas to solve this problem of mine, but I could use some input. We all know that with a boost controller you can increase the amount of boost the turbo will produce before bleeding pressure off the wastegate. That's great and all, but what if one wants to go lower than the preset pressure? A boost controller won't let you do that.
The turbo I'm using - which is a Mitsubishi unit - is internally gated and it's preset to something like 8 or 10psi. For initial tuning and "just in case" purposes, I'd like to get the waste gate to open at around 5 or 6psi. From there I could always use a boost controller to increase pressure as things progress. The turbo I'm using will support 20psi all day long and I'll never see that, so I'm good there. But since I'm doing mechanical tuning (I know, HPT would be better) I'm going to need to get the bugs worked out, and also, if for whatever reason I need to keep the car out of boost, maybe something goes wrong and I need to limp the car home or whatever, I want to be able to do so.
Now, for the solution. Or possible one.
One idea some friends and I have come up with is adjusting the actuator rod length. This I believe will require cutting the rod and adding threads to make it adjustable in length, sort of like a tie-rod end.
Another is to switch the internal spring, or modify the stock one. But how to know what spring to use, that's the trick.
I already have a neat little trick to test everything. A friend of mine used this method on his Volvo where he used a bicycle pump to put pressure on the actuator, and then he adjusted the pressure the actuator opened the gate at. Not sure if he had to adjust the spring or the rod, but it worked lol...
Discuss...
You can NOT lower the opening pressure of an internal wastegate by using an adjustable actuator rod. Lowering the tension on the rod (lengthening) just opens the wastegate before in boost, causing an increase in spool time. As far as swapping out the 'spring', I'm not so sure it even has one (I always thought it was just a diaphragm that stretched). If it does, picking the right spring would be easy, but you wouldn't be able to re-seal the wastegate (welding would melt the rubber and cause leaks = overboost).
A buddy of mine wants to use a spare T25 on his D15, but the gate is too high, so we were contemplating solutions this weekend.
fortune cookie say:
better a delay than a disaster.
Well, there was something I read somewhere about "tapping" the wastegate actuator to bleed off pressure, or make it open sooner, something like that, but I couldn't find anything about how to actually do it or how it works.
Changing the length seemed feasible, since - on the 14B anyway - shortening the rod length actually lets the wastegate hold pressure above the factory preset. In fact most of us VR4 guys will put a slight bend in the rod, and that alone will net 15-17psi almost every time. On the JDM we've been working on we bent the rod and it'll hold steady at 16psi all day long.
The other thought, and another one of my friends thought of this, is to just set the BOV to a lower pressure, but I'm not sure that will work teh way I want either. If I do it that way, then no matter what pressure the wastegate is at, I won't get over the BOV's pressure unless I changed the spring in the BOV itself.
buddy of mine did adjust the wastegate arm on a mitsuturbo for his civic and it worked great, but i don't remember if he lengthened or shortened..
i would think shortening the rod would yeild less boost, since it would take less time to open, and less pressure..
lengthening it would increase the boost.
search on HMT its been done there all the time
also one of the turbo companies sell adjustable wastegate rods, just don't remember which one
Shortening the rod increases the boost as it holds the gate longer. Did he do his to lower the preset or did he raise it? Most people raise it. I need to lower it. Or want to, whatever way you want to look at it.
he wanted to lower it,i beleive it was a mistu t25
The T25 is from Garrett. First Gen DSMs (and GVR4s) had MHI 14B turbos, Second Gen DSMs had Garrett T25 turbos (which are way smaller). Same concept, though. Both were internally gated, and I managed to get the info from some archives on the GVR4 website that the actuator itself, on the 14B anyway, is set for 7psi, and the factory boost control lets it run up to 11psi. But like I said, bending the rod nets 15-17psi without any modification to the boost controller itself. I'd imagine the T25 would have close to the same results.
DCStang67 wrote:Here you go. This is all the information you need to lower the pressure on your wastegate.
Lowering your internal wategate pressure
That's one way of doing it lol. I looked up that Honda web site too and found some info there too. One of the guys there did what I was talking about with the threaded rod and an adjustment nut. Said it works just peachy.
You can always replace the whole thing thats what i did. I got lucky and found one on Ebay that started at 5 PSI base and i was able to shorten the rod for more if i like. Keep Looking on the web and see what you come up with....Heres one i found in 3 mins of searching.....
Actuator
Hope that helps
Not a bad idea if it'd bolt up to the 14B. My girlfriend's brother told me he could take mine to work and do the threading and all that for me. His shop has all the tools and what not, it makes sense to let him do it for me. He thinks he can get it down to 4 or 5psi, which would be plenty low enough. Then a boost controller should let me get it up to 8psi easy, and then once the engine is built to handle higher boos pressure, I can readjust the rod length. Simple.
The problem with lengthining the 8psi actuator is it leaves the wastegate open a littleat all times, which makes the turbo work harder in the lower boost area by spinning faster than it should to make the same amount of boost. This will also create more lag time.
And I'd agree with you. Keep in mind I'm doing this to get an initial tune on a lower amount of boost so I can work out any issues, and as a fail safe should I experience any problems and I need to limp the car home.
ln2johnny wrote:Well, there was something I read somewhere about "tapping" the wastegate actuator to bleed off pressure, or make it open sooner, something like that, but I couldn't find anything about how to actually do it or how it works.
That would raise pressure, just like a bleed-type MBC.
ln2johnny wrote:The other thought, and another one of my friends thought of this, is to just set the BOV to a lower pressure, but I'm not sure that will work teh way I want either. If I do it that way, then no matter what pressure the wastegate is at, I won't get over the BOV's pressure unless I changed the spring in the BOV itself.
The problem with using the BOV to control boost is that the wastegate will never open, so your turbo will be spinning full-speed, shortening its life, and giving you VERY high IATs since it will be way out of it's efficiency range.
DCStang67 wrote:Here you go. This is all the information you need to lower the pressure on your wastegate.
Lowering your internal wategate pressure
It looks like that setup would raise the pressure since it's pre-tensioning the actuator (the gate may start moving at 5 psi, but that doesn't mean boost will stop there once it's installed). Interesting though, I may have to think about that one a little more.
Deekster Jones wrote:You can always replace the whole thing thats what i did. I got lucky and found one on Ebay that started at 5 PSI base and i was able to shorten the rod for more if i like. Keep Looking on the web and see what you come up with....Heres one i found in 3 mins of searching.....Actuator
Hope that helps
I was using a 6-7 psi wastegate I bought on ebay when I blew my motor on
9psi...
fortune cookie say:
better a delay than a disaster.
'Sup Josh. The one with the spring from what I can tell is basically the same theory as the idea of lengthening the rod. By holding the gate open a bit, you allow some of the exhaust gases to escape, this limiting the speed teh turbo spins at, thus decreasing the amount of boost it produces. I wouldn't use a spring, either, but if it works for him who am I to judge.
In your original response you stated that removing tension only will increase spool time, which is something I completely agree with. The trick here is to not to completely remove any tension so that the gate won't open at all, as we both know that'd be really bad, but rather to coax the gate to open at a lower pressure. We tried it on one of the spare turbos last night. We cut the rod in half, removed a bit of material, thread it on both ends, and made an adjsuter similar to that of a tierod end. We tested it with a pump and a pressure gauge to simulate a boost conditon, and it works that way, so hopefully it will work on a car. We managed to get the gate to open at 4.5psi rather than the preset 7psi. We also adjsuted the gate back as short as we could, which was only slightly longer than the original length, and the gate opened at 8psi. I'm hoping to put it on one of the VR4s this weekend so I can actually test it on a motor. If it works on the VR4, then I'll stick with it.
Sorry, the rod is SHORTER than the original length when adjsuted to it's shortest length.
I need to renew my membership dammit.
I just figured out why the springy-thingy kind of works. I say kind-of because the effect from the spring will only apply when the gate first starts to open. The more it opens, the more the gate is normal, so the max boost should remain the same (or very close). Using a longer (stiffer compressed) spring would lower max boost, but just like lengthening the rod it will hold the gate open a tad before boost hits.
I had trouble following what you guys did with your gate, you just used a standard style threaded rod (no spring)? That wouldn't change the pressure of the gate (not lower at least). Remember, the exhaust pressure will push against the internal flapper, so even if the extended arm is still 'sealing' the gate during your pressure test, when it goes on a car it will still increase the spool time because some of the exhaust gas will be able to bypass the turbine. You must have
some tension on the rod to make sure the gate seals.
Shorter arm = higher boost (negative side effect being the gate might not fully open = boost spiking)
Longer arm = lower max boost (negative side effect being a longer spool time)
fortune cookie say:
better a delay than a disaster.
ok for myself i bought an external wastegate on ebay for 100buck and it works fine,maybe you should consider this too, on ebay you can get a external wastegate with a 6psi spring in it if you want for 100 dollar that's not much for something that will be safe
http://cavalierdomination.monchar.com
Steven Lemay wrote:ok for myself i bought an external wastegate on ebay for 100buck and it works fine,maybe you should consider this too, on ebay you can get a external wastegate with a 6psi spring in it if you want for 100 dollar that's not much for something that will be safe
I can't wait until that knock-off fails on you. This thread is about internal wastegates, if he wanted an external he would've asked, right? Not everyone has room, or the manifold for an external., and not everyone will risk their motors on low-quality ebay knock-offs.
fortune cookie say:
better a delay than a disaster.
OHV notec wrote:Remember, the exhaust pressure will push against the internal flapper, so even if the extended arm is still 'sealing' the gate during your pressure test, when it goes on a car it will still increase the spool time because some of the exhaust gas will be able to bypass the turbine. You must have some tension on the rod to make sure the gate seals.
Shorter arm = higher boost (negative side effect being the gate might not fully open = boost spiking)
Longer arm = lower max boost (negative side effect being a longer spool time)
The negative effect is a slower spool-up, yes. That part sucks but it comes with the territory I guess. But in a way that's where the lower boost comes from. Letting exhaust gas bypass prevents the turbo from reaching max speed, thus in turn lowering boost pressure. Since the turbo I'm using is just big enough to provide the boost and flow I want, the lag isn't much of an issue for me. There
should be enough tension to still hold the gate closed for the initial spool, but of course if there's not, then we can make adjsutments, and if needed, use a spring to supply tension. I'm on a learning curve, here lol.
Again I want to clarify that this is only being done as a way to lower boost pressure for the initial test and tune. Since I'm going the DIY route with the parts I'm using and the install is being done by myself and a few friends, I want to make absolutely sure everythign works before I run the higher boost.
ln2johnny wrote:I want to make absolutely sure everythign works before I run the higher boost.
Wish I would have thought of that 3 1/2 yrs ago...
fortune cookie say:
better a delay than a disaster.
