[javey]

Well, to start, I would like to ask about tires. Now I know quite a bit about mechanical, but tires are a little bit different, and I understand about the numbers, but other than that they are a bit tough to understand. I recently bought tires, and then I read on the door that the tire size is a P205/55R-16, however the tires I had on there before, and the ones I have on there now are a P225/50R-16. Is this going to be ok, or are they going to wear faster, or be any problems at all?

Secondly, I have been having a boost problem. Here is my issue:

Took the car to a mechanic (and he is a reputed one) to have the motor swapped. I would have done it myself, but I really have only swapped one motor before and it was a nightmare, and I needed my car back ASAP. So he put in the new motor (and transmission if it matters) and hooked it all back up. So I also asked him to boost leak test it, which he said he did, and he said he set my MBC at 15. Now here's the problem. Every time I am idling, etc. the vac is good, at like -20. I've put all new hoses on, so no leaks. But when I get into boost, it will only hit like 5 and it will peg off of the 5 continuously. What the hell could cause this? Everything seems fine and dandy that I have checked over so far, so I don't see what could be causing this issue...

Three, I have the wrong transmission in my car. See, I bought one of those "JDM" motors off of ebay (which should have been a clue, as the eclipse wasn't made in Japan)...and it turns out long story short I bought a Mitsu. RVR motor/trans. It's all installed, and runs fine, other than a CEL about the transmission, and not having that last gear because I don't have a lockup TQ converter, but is this going to do any damage to my diff. or anything running it like this? It was expensive to do all of this for me, so I don't have money to change out the trans right now...when I get the money I will. But what do all of you gurus suggest? I'll take any help I can get!

Thanks in advance,

Javey

 

[javey]

Second part is solved by me, I checked and my wastegate arm had fallen off, or he never put it on...so I epoxied it on and I hope it holds until tomorrow, when I can buy some JB Weld (the pin broke off, and I don't want to take apart the whole car to get it out so I can work on it and tap the pin out..). It should hold I hope. I just won't get on it much. So any suggestions for the other 2?

Javey

 

[i need a dsm]

Only suggestion I got is why you bought a JDM motor YOO

Motor swaps are pretty easy.. unbolt things and wiring

The pin on the wastegate arm fell off and its stuck in there?

No the tire size wont really effect anything, just the MPH barely at all. I mean you see trucks on dubs all the time, do you think stock wheels with a dif tire is really going to effect it?

As long as you have all the same tire size and not mixed matched them you should be ok. If it was FWD, then I would say go for it, but having an awd, you don't want to fuck around..

 

[javey]

Well now that I put that arm back on, my car runs like SHIT! Seriously, it will build up to 17 psi, but it loses power bigtime past vacuum, and sounds like it's shooting the boost straight back out, it's very loud like I'm riding in a airplane! I don't know what is going on. I don't have any vacuum leaks, my turbo has NO shaftplay, and yet I have this issue. Anyone have suggestions? I'm going to look now as we speak, but I doubt I'll find anything useful outside...

 

[i need a dsm]

Exhaust leak? Hows the idle?

Boost leaks? Everything hooked up right?

 

[javey]

Ok well I believe I solved my issue. The damn UICP hose clamp was loose and now it seems to boost fine to a point, but it still doesn't seem like it has as much power as it should. Also, the BOV line when in vacuum is all sucked in, is that just a result of cheap hose? The gauge goes to like 15, and then starts pegging. I'll post a few vids, but I'd like some opinions:

http://www.youtube.com/watch?v=XeFnWOJcY5M

http://www.youtube.com/watch?v=VkfnSxlcukA

I don't really know where to go with this. Anyone have ideas? I'd really appreciate it.

Javey

PS, I do have an exhaust leak at the first flange to the cat, but I don't think that is the kind of exhaust leak you are referring to, no? Idle is great.

 

[need2fix]

Well now that I put that arm back on, my car runs like SHIT! Seriously, it will build up to 17 psi, but it loses power bigtime past vacuum, and sounds like it's shooting the boost straight back out, it's very loud like I'm riding in a airplane! I don't know what is going on. I don't have any vacuum leaks, my turbo has NO shaftplay, and yet I have this issue. Anyone have suggestions? I'm going to look now as we speak, but I doubt I'll find anything useful outside...

How are you tuning the fuel?

If it's getting more air than the ECU can/wants to deal with, then it will either run retardedly rich, and start popping and bogging, or it will run really lean... which makes a good good pull... until the BAM.

EDIT: If it feels like it's revving, and then hitting a wall, you're running rich.

 

[javey]

How do I tune the fuel? All I wanted to do was add a MBC and up the boost a few pounds to like 15. It's a t-25, I don't want to get too crazy. Is 15 psi too much?!

 

[i need a dsm]

You need a piggy back or dsmlink or whatever to tune the fuel system bro. You got stock injectors, pump, turbo etc im guessing then?

 

[javey]

Yup all stock stuff as far as that, all I really have is boost gauge, hard UICP, 1g bov, dejon intake with K&N filter, and that's all I can think of. That's why it caught me off guard about tuning fuel right now, when my goal really isn't to make a junkload of HP, but to add a little snappiness to my car. I shouldn't have to tune any fuel for 15 psi on a t-25 should I?

 

[i need a dsm]

YOu don't need a tune right really. Sounds like you got boost leaks for sure and some exhaust leaks

IF your car sounds like shit, then make sure every exhaust component coming from the exhaust manifold to the downpipe is tightned down right

And make sure all the IC piping is tight!

15 psi on stock everything is the max I would do, anymore than that is just hot air and you are risking blowing up the motor due to detonation/knock

 

[javey]

Well since it's running like ASS, I'm going to take the wastegate arm off again and let it drop back down to 6psi, since anything above that that I run now, feels wrong. Until I can have a look at it properly.

Javey

 

[AXiS]

What you are aiming for on the tire size is to keep the overall circumference the same as the stock size to keep the speedo as accurate as possible on the car. The stock tire was 205mm wide with a sidewall proportion of 55%. The other tire was 225mm wide with a sidewall of 50%. If you do the math, those two tires are about as close as possible to being the same circ. as you can get within reason. Of course other things will come into play such as the width of the rim the tire is being put on, but all things equal they are very close, while getting more tire width on the 225. Here's a website that you can use to compare different tire sizes. http://www.miata.net/garage/tirecalc.html

 

[javey]

Also, if it helps diagnose, it will go into boost in park. Why would it do that?? It will hit like the full PSI that it would in drive...

 

[javey]

Does anyone have any input? I'm still lost here...Boosting in park, could it be a bad wastegate alltogether? I don't know TOO much about these turbos, that's the thing. Any help is greatly appreciated.

Javey

 

[91Bluebird]

The 225 tires are 2 sizes wider than stock 205's which is a significant increase in width (2 sizes wider) and should definately improve handling UNLESS they are 'H' rated crappy non-performance tires and the 205's were some really good 'V' or 'Z' sticky handlers. Your gas mileage will suffer a bit but I'd take the 225's anyday over 205's unless it's a situation like I mentioned.

When you mentioned getting 5 lbs boost the 1st thing that came to mind was your Bosst control solenoid (BCS) was acivated or not hooked up properly or something to that effect. It's a safety feature that when engine knock is detected, or perhaps even phantom knock, your knock sensor sends a signal to the BCS that linits boost to 5-7 lbs to protect motor from damage so make sure that's hooked up right or bypassed depending on your application.

1g turbo cars with A/T's did not come with lock-up torque convertors and 1g non-turbo a/t's did and I've owned both. The difference is at highway speeds and when equipped with lock-up TC engine speed drops 3-400 rpm at 50+ mph when in 4th gear so your engine will be turning 3-400 rpm higher without one so gas mileage will be noticeable lower (approx 3 mpg less) on a long highway trip. Around town it will not matter and mixed driving will not matter much at all. The thing is if you have an awd 1g without lock-up your rpms will be really high like 3800 @ 80 mph and on FWD 1g turbo definately better but still a high-ish 3500 @ 80 mph and that's vs 3100 @ 80mph on a 1g N/T or 2g turbo fwd. So cruise at 80 mph on a long trip and your gas needle will sink like a stone lol but keep it down to 70 or lower and you'll do much better. My 1g turbo FWD without lock-up gave me 23 mpg in mixed driving while racing around everyday and my n/t with lock-up only does 1-2 mpg better with a very light foot so go figure. Also without lock-up since engine speeds are higher in top gear over 50 mph you'll get good engine braking when you lift off the gas so the car will slow down significantly faster which makes for much better car control and if you're an enthusiast driver like me it's definately a good thing..

 

[UPSJoKeR]

Ok when you say it goes in boost while in park what exactly do you mean? its supposed to go to like 0-5 psi for a split second since you are creating exhaust pressure which is turning the shaft on the turbo therefore creating a little bit of boost. not if its just boosting then thats not right.

 

[javey]

I boost up to like 15psi in park, and hold it.