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I did a compression test today on my 1UZ and noticed that the throttle plate is normally open without depressing the accelerator or pulling on the throttle cable. Then I looked inside and there's another throttle plate but closed. Looks like the photo below, is that normal?
Also, what is that part circled in red? Could that be an A/C component?
That first throttle plate is for TRAC (traction control). It is normally open and closes when needed to reduce power and skidding. It supposedly helps, but I always thought that's what modulating the gas pedal is for.
I'm not familiar with the item in the second pic. It doesn't look anything like my AC system. Is your SC a '92? That would be the earlier freon setup, if so, and I'm not sure how it differs. Did you follow the lines to see what they connect to? It looks like it has a test port on top.
t2d2 is right about the front plate being traction control, mine looks just like it, itll start closing to restrict air no matter how much gas youre giving it. As for the second picture, im not exactly sure, I have it on mine and all i could see from a quick look is that its made by denso
Thanks for the replies everyone! I should get an FSM to help me get acquainted with this car. I have been a Nissan guy for 25 years, my last car is a twin turbo Z32. I picked up this SC400 2 weeks ago because I've always wanted a Japanese v8 car but I've always had a thing for classic 90s Japanese cars especially Nissans and Toyotas, hence I got this car.
Also, as I was taking the intake pipe out in preparation for the compression test last weekend, I noticed this odd looking thing attached to the plastic intake pipe. I've never seen anything like it. See pic below.
I'm thinking that this might be some kind of buffering chamber to help quiet down the air charging into the TB. But for the sake of making it easier to remove the plastic intake pipe while performing maintenance in the future, I'm thinking of replacing this part. Perhaps get a pcv pipe from home depot and attach silicone elbows on both ends. I want to retain the stock air filter box as this is already a cold air intake setup.
It's a resonator. A few of us have removed it. I haven't noticed any ill effect, although I later learned that they're more for intake tuning (at least on some cars) than noise reduction. See: Helmholtz.
the canister circled in red is part of the traction control system. I believe its the accumulator or something like that.
cars without traction control do not have them, so its a sure give away the car has traction control, along with the second tps and throttle plate in the throttle body (Cars without trac do not have the second tps or butterfly in the throttle body and are a little shorter).
Trac control was a popular option on automatic models, and for all manual sc300's it was not even an option as they all came without traction control.
I changed my mind about replacing the intake/resonator after reading this: http://planetsoarer.com/resonator/resonator.html. It goes on to mention about a couple of articles showing that big resonators tuned to specific engines free up low end power. Then the author himself did a comparison between the stock/resonator and a custom intake pipe that he made out of 3.5" pipe. His car ended up losing power and made it go slower - no performance gain and just an annoying induction roar.
On a different note, I was tinkering around the SC this afternoon and noticed this disconnected component. Looks like it maybe a coolant level sensor or something.
Originally Posted by t2d2
It's a resonator. A few of us have removed it. I haven't noticed any ill effect, although I later learned that they're more for intake tuning (at least on some cars) than noise reduction. See: Helmholtz.
Yeah, that looks like the connector for the coolant level sensor, which is the rubber cap/plug and extension just to its upper right. The PO probably disconnected it to keep the indicator from lighting up. If I remember right, the dummy light stays off with no connection, but comes on with a faulty sensor. I replaced my sensor awhile back because it was quite deteriorated and I feared a chunk would clog the hoses. (A big piece broke off in my hand at the slightest touch.) Occasionally, it lights up briefly now when the engine is cold, so I guess I know it's working...
As for the resonator, you're certainly justified in not wanting to mess with the engineer's design. Personally, I've noticed absolutely no difference without it and decided to get rid of the bulky thing one day when I was fed up with working around it and/or having to remove much of the intake tract because of it. Also, I'm skeptical of any studies showing the importance of it, because every time we modify the intakes we're affecting the factory tuning. Even if it is a measurable difference, there are a lot of variables to control for and they likely won't apply to everyone.
if your resonator does not have a crack in it then keep it, on a stock car it does seem to make a seat of the pants difference, even on an auto sc300 I had I noticed a power loss down low going from the stock to a regular pipe with a cone filter, it seemed to free up some up top noise, but not sure about more power.
Its common for them to crack over time though or leak a little, and then it will probably feel better to replace it with a straight pipe at that point, its the main reason to get rid of it they will crack there or at the "accordian" part of the plastic sooner or later.
if your resonator does not have a crack in it then keep it, on a stock car it does seem to make a seat of the pants difference, even on an auto sc300 I had I noticed a power loss down low going from the stock to a regular pipe with a cone filter, it seemed to free up some up top noise, but not sure about more power.
You changed two things simultaneously, though. Unless you built a good heat shield for the cone filter, it's pretty commonly accepted that they worsen performance on the SC.
They're all flawed studies, IMO. Look at the Planet Soarer link that dricacho provided in post #9. They talk about the tuning (low RPM torque vs high RPM power) attributes of resonators, then go on to say they found the underlying reason is the surplus of air the chamber provides because the throttle is an open/close device, not constantly flowing. However, they didn't test in conjunction with COLD air intakes designed to improve said air flow. That may very well provide the same surplus of air as the resonator.
There could be something meaningful to the data provided, but as presented, it's far from compelling. Of course, I'm biased because I removed mine (from both cars) and couldn't tell a difference. But, I also modified the intake on both cars to pull in as much cold air as possible.
I took the air filter box out this afternoon and found two rubber hoses not connected to anything. The other end of both hoses seems to run down and under the power steering pump (circled in red). Does anyone know where they are supposed to be connected too? Thanks.
04-18-15, 01:14 PM
Engine bay question
