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1G Fixing the s90 throttle body

Posted by SasaniFab, Dec 10, 2018

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  1. SasaniFab

    SasaniFab Freelancer

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    So im in the middle of upgrading my throttle body and come to the conclusion that the 74mm s90 is the best bang for the buck. The real issue is that they all leak. Ive been thinking about throwing a kit together to allow guys to repair them properly. For 200 bucks you really cant beat them. Can we keep a page up for part numbers and solutions to repair these? Im waiting for my 74mm to get here so i can tear it apart and get measurements
     

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  2. 95GSXracer

    95GSXracer DSM Wiseman

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    My question here is always, how much does that leak actually matter? Assuming speed density, I can definitively say that a ~3/8ths hole in my intake manifold at 45-50 psi has no effect on performance at all. The mass airflow through that leaks was calculated at a fraction of one pound per minute (if I did it correctly, LOL). Just something different to think about.
     

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  3. ThunderChild

    ThunderChild Supporting VIP

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    Not to sound like the snarky kid, and it's not a direct comparison, but that makes it sound like a pinhole in a tire shouldn't be addressed because it won't affect things for a majority of the situation. Also, not everyone runs speed density.

    I think it's a good idea to try and improve the s90, no reason a non-leaky, bolt-on, large size TB is a bad thing, especially for the price. I've been contemplating an s90 for some of my side project tinkering, but the horror stories have prevented me from buying.

    Biggest thing I am curious about is the shaft itself, isn't it aluminum as well? Depending on the alloy that makes me curious how it may hold up to seals and grooving over time, and if it may be optional to change the shaft to steel?
     

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  4. motomattx

    motomattx Proven Member

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    A leak would mean more to a person that wants a good idle I suppose, unless you wanted to try and tune around it, Im sure I have a few small ones here or there that I dont notice but with standalone I likely tuned around it.
     

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  5. 95GSXracer

    95GSXracer DSM Wiseman

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    It doesn't really affect idle either, unless it makes it too high with the BISS closed all the way, or forces too closed a throttle position and it binds. Air is leaked on purpose for idle, after all.

    I'm not trying to suggest any particular course of action here, just bringing up an odd point that few people are aware of. I've seen hundreds of guys chase tiny leaks for years when it just makes no difference in so many cases. With MAF, by all means, chase those leaks. And I do agree that fixing the leaks can't be a bad thing. Just don't expect the power gains the internet promised us all 20 years ago. :D
     

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  6. 95GSXracer

    95GSXracer DSM Wiseman

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    And now that we've gone way off topic (sorry), I should also add that a rare few leaks are an issue on speed density. Leaks that affect the MAP sensor itself, and leaks that affect individual cylinders (lower injector seals, IM gasket, etc).
     

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  7. SasaniFab

    SasaniFab Freelancer

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    The leaks that occur on the s90 in my case were very severe. A lot of users claim that an audible hissing sound can be heard at idle. The shaft seals in these throttle bodies are atrocious, very poor quality. The website for their company doesn't work anymore, for me anyway. The s90 is the only throttle body available to us that is fully bolt on....provisions for iacv and tps. For 200 bucks its well worth fixing imo. Anybody have a 74mm they want to send me so I can take some measurements and get something together? I have access to a machinist also......Id like to fix these damn things
     

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  8. ThunderChild

    ThunderChild Supporting VIP

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    @amsrn13 I may be inclined to purchase one and send it to you for prototyping, depending on some details. Pm me.
     

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  9. motomattx

    motomattx Proven Member

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    These are what I was talking about and specifically at idle where it can cause map output to be all over the well... map and a high idle where random air is bled into the system thats not wanted.
     

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  10. 95GSXracer

    95GSXracer DSM Wiseman

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    Leaks like that are extremely rare, but they do happen. Leaks at the FPR are another potential source of actual problems. When it comes to generic leaks like those at the throttle shaft seals though, I think people would be surprised to learn just how little it really matters. I've got two cars with throttle bodies that don't even have any shaft seals at all, and they both happily idle along at 900 rpm. A 0.1 lb/min leak on an engine that needs 0.6 lbs/min to idle really is a nonissue. You could also make the point that if stock throttle bodies have supported enough power for 8 second passes, why "upgrade" to something that's allegedly worse? The public perception of what size throttle body is needed is so warped that people are often surprised I still run a 75mm throttle body on my car. I'm not surprised, because I know there is no measurable pressure drop even at 120 lbs/min (this of course is the wrong measurement to be concerned about, but it's something most people can relate to). If someone is running a MAF or some other stockish setup that is sensitive to leaks at the throttle shaft, they certainly don't need a bigger than stock throttle body. Just stick to a stock throttle body designed by OEM engineers that uses shaft seals, rather than taking an aftermarket unit that seems to be a POS by all accounts and cobbling some seals onto it. To put it another way, if you have a setup that "needs" a 74mm throttle body, you probably also have a setup that doesn't care about throttle shaft leaks and you can move on to more important things. Or, at the least, try it as is and see what happens.

    So my first thought when I read this thread was that it would be a waste of time to polish that turd. But I don't mean that in a bad way! I've wasted time on a lot of projects and still had fun doing so. I would never want to discourage anyone from spending their time and money however they like. I just like to dig a little deeper into these seemingly boring and mundane topics and see what kind of discussion comes out of it.
     

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  11. motomattx

    motomattx Proven Member

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    ^^^ I very much agree with you on those points, I have never even tried to chase throttle body leaks even on a stock setup.
     

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  12. SasaniFab

    SasaniFab Freelancer

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    For the money i think the s90 is a great deal considering its plug and play even if the benefits arent tremendous.Most guys are spending their money either sending their oem throttle bodies out or replacing the seals themselves anyway. Im genuining interested in offering a solution for the guys who purchased them.
     

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  13. SasaniFab

    SasaniFab Freelancer

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    I wish i took a video of me boost leak testing my 70mm. I thought i was doing something wrong, I couldnt even pressurize the system it was so bad. Aftet replacing the seals it didnt leak on bit. 20 bucks and a perfectly working tb..... not bad for 200 bucks...
     

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  14. SasaniFab

    SasaniFab Freelancer

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    When I recieve the throttle body I will be taking measurements and ordering some seals, i may even machine a new shaft. We will c
     

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  15. ThunderChild

    ThunderChild Supporting VIP

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    My reasons for being interested in this are for a custom project in which a larger throttle opening (or at least not bottle necked) is highly beneficial to the overall packages function. While I could use another 3" TB, having a PnP TB would be highly beneficial.

    It's interesting to see how the community can be so focused on things like BLT, TPS adjustment and minute things that affect the overall performance and reliability of our vehicles, yet the opinion of a leaking throttle is passed off as inconsequential. Granted I realize most ppl running throttles this size dont really care about daily drivability due to the cars being dedicated race status generally. But I don't like to settle for that in my situation, kind of a "have my cake and eat it too" scenario, not wanting to make that particular compromise.

    Seems like a worthwhile endeavor to me to have a quality, non-leaking, bolt-on large TB.
     

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  16. 95GSXracer

    95GSXracer DSM Wiseman

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    I'm not saying throttle shaft leaks are just an acceptable compromise for a race car, I'm saying in my experience they don't matter at all in many cases and a perfect idle is still attainable. I know, it sounds outrageous. Don't take my word for it, try it yourself. And at any rate my own car runs 7s and it has a rock solid idle, and cruises around the pits in closed loop with good fuel trims and good throttle response. It even cold starts reasonably well on E85/methanol, once the pump primes. Some race car guys get lazy with the low end tune, while the WOT tune is easy to get right, I get it. And some guys even think it's more of a race car if it runs like total crap. I like my race cars to run like street cars, just faster. As a tuner, if it idled and ran like sh**, I'd be too embarrassed to show up at the track. :D I do also build and tune a lot of street cars, hundreds of them over the years, and have lots of good examples there. But again, I digress. Do whatever makes you happy. I'm sticking around to see how the solution here turns out.
     

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  17. SasaniFab

    SasaniFab Freelancer

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    Big thanks to tametalon92.... recieved the throttle body today. Its nice to know you can trust people in the world. Once I get it broken down with measurements Ill post everything up. If I fail or damage this unit..... My friend will be getting his money back. I dont plan on failing though
     

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  18. brian9397gsx

    brian9397gsx Proven Member

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    Glad to see your perseverance. I for one would probably be interested in a fix up kit if you get one going. I get it I dont need a bigger tb but damn it I kinda want one LOL.
    That's kinda the mantality of a lot of car enthusiasts upgrades. I really like the look of the s90 over stock and I've gone through a lot of trouble making mine look good. But yeah LOL
     
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  19. SasaniFab

    SasaniFab Freelancer

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    Managed to get it apart without breaking or stripping anything. The tb shaft is very very weak, im gunna try to get a stainless shaft made. The tb leaked out of the box, before i took it apart i bolted it down to a aluminum plate and pressurized it. The most serious leaks occur at tps sensor side. The opposite side has provisions for a seal. I noticed they also use some type of compound around the shaft were the bearing seats. Feels like silicone. The bearings are koyo surprisingly, I was thinking maybe adding a seal to the tps side? Going to speak to my machinist this weekend
     

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  20. Vegas smith

    Vegas smith Proven Member

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    This all seems very worth it :)
     

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  21. gdb1039

    gdb1039 Proven Member

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    I must be lucky, I just installed a 74mm s90 on my car yesterday and it BLT tested to 30psi with no leaks. How much pressure has this TB you have been leaking at?
     

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  22. SasaniFab

    SasaniFab Freelancer

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    Some people are lucky, some are not......Prob depends on how well the person assembling it seals the shaft. The tolerances on the shaft are a bit loose, they make up for it by using the sealant. Im gunna try to add a seal to the tps side
     

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  23. ThunderChild

    ThunderChild Supporting VIP

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    Now now, haha.
     

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  24. jakelandry

    jakelandry Proven Member

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    I'm glad to see there are still people who care to do things right but the truth is this is stepping over dollars to pick up dimes. 98% of dsm's are running around on such terrible tunes that the small inefficiencies like these are negligible. If you're the type that doesn't half ass a single thing then sure this is definitely the way to go, but our forum is the worlds worst about worrying about small stuff when their cars are literally falling apart.
     

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  25. ThunderChild

    ThunderChild Supporting VIP

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    Totally agree with what you say, but mechanically I'm pretty anal about how my engine uses or leaks fluids/air. I don't like leaks. Hence why I'm invested in this project.

    Most may not care given the situation, but it means a lot to me, and tho I could do this myself, @amsrn13 seems to have the drive and time that I don't currently. So I'll supply parts while he does the leg work for all of us to get a no-leak, cost effective TB.
     

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