Guest bastaad525 Posted November 12, 2004 Share Posted November 12, 2004 Okay... I've asked about this issue many times... and gotten a lot of good info and oppinions on the hows and why's of why it's happening, but really... even knowing all this, I still can't decide which way I should do this, and it's driving me nuts. About how to route my boost controller/wastegate actuator signal. I've already gotten very in depth with the problem, and guys here have given me explanations and suggestions on parts of the issue. Now... it really boils down to one of two choices... and being the pro's and con's are roughly equal, IMO, this is basically a poll to see how you guys would do it if you were in this exact situation... give me a 'majority oppinion' so I can just set it and leave it once and for all. For anyone who doesn't already know, I'm running the grainger valve style manual boost controller. Here are the choices: Choice 1: run it like stock. Get the signal from the compressor housing. Pros: - Most accurate source for the signal (though.. I'm not exactly sure HOW this is a pro?) - Fast wastegate response, very little boost spiking, ~1psi Cons: - Seems to spool a little slower... wastegate is open fully and full boost is reached at the compressor right away and the MBC/wastegate opens, but it takes a split second longer to actually fully pressurize the intake - Boost fall off as revs increase - This seems to be very specific to my setup. I'm not 100% why it happens... the best theory I've been given is that for some reason I'm getting a lot of pressure drop across my I/C as revs and flow go up. This is the question I've already covered in depth here in the past. At any rate.... in a 4th gear pull, boost falls off steadily, at a rate of about 1psi per every 1000rpm. I have it set to run 14psi initially at 3000rpm. Power definately falls off noticeably with the boost. At 6000rpm, I'm estimating I'm losing at LEAST 10-15hp for those 3psi of drop. But it FEELS like much more... like the car just falls flat on it's face... very unimpressive. Choice 2: run it from the intake manifold Pros: - Strong vacuum signal when throttle is closed (shifting), closes the WG tight and fast, presumably helps keep the turbo spinning between shifts. - Boost does not fall off, holds steady 14psi to redline, power feels much better above 4000rpm. - Seems to spool up to full boost faster, as the wastegate cannot open until 14psi is fully reached in the manifold, but... Cons: - ... there is much more initial spike because the turbo just keeps on spinning past 14psi during that split second it takes the manifold to pressurize and open the MBC/wastegate. I get about ~2-4psi of spike depending on the situation (gear, rpm when floored) - IF the pressure drop theory is correct, that means the turbo must keep spinning faster and faster, producing MORE boost at the compressor housing, to maintain a steady boost level in the manifold as revs increase. The turbo could possibly be spinning 17-19psi worth of boost under certain conditions (spiking or whatnot). It's driving me nuts... I want the extra power, and the car definately pulls better when running the signal off the manifold. But at the same time, I dont want to send my turbo to an early grave by overspinning it, IF I'm overspinning it. And I have no idea how this is effecting the charge temps but I'm gonna guess, running it from the manifold is probably causing temps to go way up, since the turbo is possibly boosting 2-3 more psi than what's actually getting to the manifold. SO what the heck should I do????? EDIT: I almost forgot, one other pro and con for running the signal from the compressor: Pro: lower boost at higher revs may be giving some added safety margin from detonation Con: Boost falling off also means the RRFPR/FMU is providing less fuel as revs increase, possibly increasing the chances of detonation. Quote Link to comment Share on other sites More sharing options...
wheelman Posted November 12, 2004 Share Posted November 12, 2004 If it were my decision to make I'd run it with the signal from the manifold. Seeing as I don't have a turbo car and it's not my decision you should do it the way you feel most comfortable. I do think you're over thinking the situation though. I guess as a side note for the sake of safety I'd drop the max boost 1 or 2 PSI just to play it safe. Although my Z won't be a daily driver so I wouldn't be playing it safe. Wheelman Quote Link to comment Share on other sites More sharing options...
mobythevan Posted November 12, 2004 Share Posted November 12, 2004 When problems like this bother me I take a more scientific approach, like adding a second boost gauge for testing purposes. Run the signal from the intake manifold and then add a second boost gauge at the compressor outlet to see what is really does(is it really going 2psi higher or 10psi higher at the spike?). Gauges are pretty cheap. Maybe you need a buddy to help watch all the output. That may not be totally accurate with cheap gauges and people doing the logging, but hey, it would add some insight into the issues or non issues. I did this in a round about way with my setup using MSnS to log before and after IC install to measure pressure drop and give me an idea how much more psi the turbo is pushing at the compressor outlet than the intake manifold. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 13, 2004 Share Posted November 13, 2004 I figure the boost controller is acting as a sort of boost gauge itself. It's set to open at 14psi no matter what. I dont change the setting at all when I switch between the two different routing methods. Since it holds a steady 14psi (as read by the boost gauge, which gets its signal from very close to where I run the MBC from) when hooked to the manifold, I have no reason to believe it's doing any differently running from the compressor... so it should regulate 14psi at compressor as well. Whatever difference the boost gauge reads from 14psi, should be the true difference in before-and-after I/C pressure. Someone else had suggested the second gauge to me... and I would like to try it, if only because as you mention, I would be particularly interested in seeing what it does during the intial onset of boost and the spike. But for me, $50-75 is a lot to pay just to answer that question. Wheelman - I overthink every situation in regards to this damn car Turbo's are a real headache for me... because it's always "I know I could squeez some more power out of it... but... is it gonna blow if I do?" Essentially having a knob marked "Horsepower +/-" is driving me nuts I'm gonna start crazy glueing stuff in place Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 13, 2004 Share Posted November 13, 2004 Are you bleeding off a little pressure between the MBC and wastegate? I used an adjustable bleeder to let a little out. As far as lag, either way should be the same as the wastegate is held shut on it's own till atleast 7psi. On mine I came off the turbo as it's closer. Pressure is pressure. On integral wastegates you'll have more a more accurate setting by running an extra spring to hold the wastegate shut. I have never had any boost creep or bleed down using that method but now that I have the external with an 8 psi spring and the MBC it's become an issue for me too at higher boost as the RPMs rise. As the RPMs go up there is more back pressure working against the spring. I'm still waiting for the 15 psi spring to come in Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 13, 2004 Share Posted November 13, 2004 the MBC has a small hole (.020" I believe) drilled into the outlet side of the valve to bleed off some pressure there, and too keep the valve from being held open between shifts. I dunno if that's what you mean. I dont understand what bleeding off any more of the pressure there would accomplish, other than causing it to open at a slightly higher boost (since you're bleeding some of the boost signal off), and skewing my a/f ratios ever so slightly I thought drop might be due to backpressure as well, but doesn't make sense as far as... why can I get a steady boost if I run the signal from the manifold instead. If backpressure were the cause... it should behave the same regardless of where I hook the wastegate to. BTW guys... I'm always happy to get more input on the hows and why's of this whole thing... but don't forget to 'cast a vote' as far as my original question, on what you think is the better way to run it! Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 13, 2004 Share Posted November 13, 2004 the MBC has a small hole (.020" I believe) drilled into the outlet side of the valve to bleed off some pressure there' date=' and too keep the valve from being held open between shifts. I dunno if that's what you mean. I dont understand what bleeding off any more of the pressure there would accomplish, other than causing it to open at a slightly higher boost (since you're bleeding some of the boost signal off), and skewing my a/f ratios ever so slightly [/quote'] The .020" hole is what I was using the bleeder for. Subliminal extra spring for wategate Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 13, 2004 Share Posted November 13, 2004 okay... well I"m not sure what the extra spring would accomplish either... with the MBC I'm using... NO boost signal can get to the actuator until the MBC opens... Unless the wastegate actuator itself is just old and tired and is always slightly open even when no boost is present there. In that case I just need a new WG actuator. How would I install an extra spring on the stock WG actuator??? Quote Link to comment Share on other sites More sharing options...
Bluto Posted November 13, 2004 Share Posted November 13, 2004 Good luck working out something that will work well for ya. Sam Quote Link to comment Share on other sites More sharing options...
wheelman Posted November 13, 2004 Share Posted November 13, 2004 Where are you getting the boost gauge signal? Before the IC or after? If you get it before the IC then the pressure reading will be higher than the intake actually sees due to the pressure drop across the IC which would be a false reading when you get the MBC signal from the manifold. Maybe thats why you "see" a spike on the boost gauge with the system configured to control boost from the manifold pressure rather than the turbo outlet pressure. Just a thought but that spkie might not be real when pressure readings are taken from the manifold after the IC. Anyway these ideas are all irrelevant if you get the boost guage reading after the IC. Wheelman Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 13, 2004 Share Posted November 13, 2004 How would I install an extra spring on the stock WG actuator??? I sold the last turbo I had with it on. I will find something and kinda hold it up to a turbo and get a pic to show. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 13, 2004 Share Posted November 13, 2004 yep boost gauge reads from the intake manifold, after the I/C. I was figuring on 1-2psi of constant pressure drop from the I/C of course... but wasn't figuring on more drop as revs increased. I realize that either way what the boost gauge reads is going to be lower than what's actually coming out of the compressor, regarless of where I have the MBC hooked up. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 14, 2004 Share Posted November 14, 2004 Seven replies, three days, one 'vote' come on guys I need some advice here before I drive myself nuts. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted November 14, 2004 Share Posted November 14, 2004 I vote you by the MSnS and then use the new extra code with a solenoid to have electronic boost control, then I can use it when it works. Actually I say stay with the signal from the intake side. Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 15, 2004 Share Posted November 15, 2004 How would I install an extra spring on the stock WG actuator??? Ok I went to my friends and go a pic of it. I sold him my extra 7M setup for his Z. I ran this at 17 PSI' date=' wastegate diaphram is 7 psi like the Nissan one. On Nissan turbos there is enough room to hook the spring around the wastegate bracket. This is a Toyota turbo though and there isn't the room so I welded on a nut on the rod. It held all the way to redline never falling off or spiking. Cost about $5 and is adjustable from stock boost to whatever it takes to put a hole in a piston [img']http://www.geocities.com/clifton_ragland/wastegate.jpg[/img] Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 15, 2004 Share Posted November 15, 2004 Clifton - okay I still don't quite understand what that spring accomplishes... but I will say this, I dont' think it would solve my problem. You have to keep a couple things in mind in my case. The WG actuator, as far as I know, works fine... this isn't a problem with it being old or worn or just unable to cope. I say this because before I installed the I/C, and was just running the stock J-pipe, I did take my boost signal from the compressor housing, and was running the same MBC set to run 10psi. With this setup the boost never fell off, it held steady 10psi to redline. Boost only started falling off when I installed the I/C. So I'm 99% sure the boost bleeding off has nothing to do with the WG actuator not being to hold, but rather is a symptom of pressure drop as the air passes thru the I/C and piping. Since the WG actuator and boost controller are getting their signal from before the I/C, they are not 'seeing' or compensating for this pressure drop. But when hooked to the manifold instead, they do compensate for it. And when hooked up this way, the WG actuator has no problem holding boost steady to redline. BUT, since it's compensating for the pressure drop, the turbo must be spinning faster and faster to maintain steady boost in the manifold... by 6000rpm, 14psi in the manifold might be as high as 17 psi at the compressor housing. Moby - are you nuts? and throw yet another variable into the mix to try to blow something up? Heheh make me your guinea pig will you...... Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 15, 2004 Share Posted November 15, 2004 The spring applies more pressure to hold the wastegte shut until the desired opening pressure. If you add another 10 lb of tension to a 7 lb wastegate you have a 17 lb wastegate. With the spring you don't need to use the more expensive, less reliable MBC. If it was still mine I would send it to you to try. I got my new stiffer WG spring in yesterday Now I can hold 20 psi to redline It was supposed to be a 15 psi spring but is around 18. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 15, 2004 Share Posted November 15, 2004 okay lets say I did that, installed a 7lb spring on the wastegate, together with the stock 7lb spring, it would hold 14psi. BUT, there would still be pressure drop across the I/C as revs increase, and my boost gauge (reading the manifold) would still register boost getting lower and lower. The MBC works really well, IMO, it's very consistent, except that it occasionaly needs to be removed and cleaned (once every 3-6 mos). It only cost me $10 it works very similar to your description... basically it allows NO signal to get to the WG actuator until the pressure setting I have set it too is reached, at which point the ball valve opens and lets the signal thru to the actuator. So the actuator stays completely shut until that set boost level is reached. Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 15, 2004 Share Posted November 15, 2004 Dose yours initially spike and then drop down to the setting? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 15, 2004 Share Posted November 15, 2004 when it's hooked up to the compressor housing, it spikes about 1psi, only for a split second before settling to 14psi, then slowly falling off from there. When hooked up to the intake manifold, it spikes 2-3psi for a split second then settles at 14psi and stays there all the way up. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.