Is my VDI stuck?
 

So I went drag racing last Saturday for my 21st birthday. I know the RX-8 isn't a drag car, but mashing your pedal to the floor anywhere is always fun! Anyways, it provided me with the perfect opportunity to take some logs with my COBB AP in a controlled environment, and so I did. Didn't get phenomenal times, but better than my first bout last December.

Anyways! I later loaded the logs into Virtual Dyno, did some weight and SAE corrections and lo and behold! DATA! Ended up making around 184whp @8,436rpm & 120lb-ft @6,902rpm. Pretty decent methinks. That power spike after the APV opens is huge! Would love to open it up sooner!

Anyways, after peak torque, everything just goes kinda mehhh. I noticed this so happens to be right around when the VDI is supposed to open, but I see nothing happening, airflow seems to remain the same as well til later. I suspect the VDI may be stuck because I accidentally overfilled my oil recently, with HEAPS of smoke coming out of the exhaust. No other obvious adverse affects though.

So what do you think? P.S. Power spike after 8K is due to leaner AFR's, between 11.32 ~ 12.35, versus a solid 11.17 throughout most of the run.

'04 MT w/ 127K miles, 10K on all OEM ignition parts, RB Ram Air Duct, 3" exhaust w/ cutout, COBB AP w/ MM Base Map (yes, the one you first get when ordering it, no revisions made)

Your VDI is right under the UIM and behind the thermostat housing. Reach in with a screwdriver and try to move it. If it works have someone rev the car and see if it opens.


The past few days I've been playing with lowering MY APV's.

I feel the surge in power when they open in 1-3rd. I am thinking that there is a restriction on the engine and if I open them just before the flow is restricted then it will not have the lean spike that occurs when they open.

Currently I have them at 5900 and I am still feeling them, but not as much and the lean spike is not near as high.

Thanks, you can move it by hand without damaging it?

I would use the Virtual Dyno Program, if you really want to pinpoint it and can find a flat road to test on. I will be playing with my own custom tune as soon as I get another ride, don't want to be messing with my only car. I would personally try opening them wherever your torque/load peaks, if it happens before the opening. I will be moving my VDI to 6,900 to start with.

Let me know what happens!

Yeah, it should be real free and easy to move. If you have a vacuum pump you can pop off the hose and test it with that also. There is a round(gold color I believe) vacuum actuator that points toward the front of the car.

Right now I'm working off a butt dyno and just playing to see if Lowering the APV will get rid of the Lean spike that everyone tries to tune around. I figure If I can feel it open then it is a power restriction. When I get it dialed down where I don't feel it then I'll use the lean spike to get it really close.

yep, it should move freely, and if you check the diaphragm it should hold vacuum. in theory the solenoid would throw a check engine light, so it should be working

Next time dyno in the proper gear, and that graph looks all sorts of not normal!

Yeah, I figured that. I just need some who's smart enough to understand, "Look at this gold thingy while I rev my engine and tell me when it moves."

Lmao, I know! There's tuning to be done. But also...

1. It wasn't a dyno, it was drag racing :nono:

2. When I am absolutely positive I have my whole system working flawlessly, in perfect health, THEN I will dyno it! :naughty:

That's not a very good data log.

Start your run at 2500 rpm in 3rd gear ... hold to 8500+ rpm
Show Calc load and AFR along with HP and Torque

I think everybody missed the part where I said I was drag racing. If I can find a road flat enough, long enough, and straight enough - to go from 25mph to 90+mph - WITHOUT publicly looking like a dumbass, then I will.

I do have the drag log, that was just the dynamometer interpretation of it.

Get a real dyno done! You can't diagnose off a log, especially one that encompasses 2KRPM out of the entire range. For all you know their is nothing wrong with the car and your butt dyno is butt hurt over something!

Haha, I will eventually! But for now,

1. This is a much cheaper alternative, and allows me much more runs in one night.

2. I don't see why I can't diagnose off a log? It's real world data, so I'd actually prefer it.

3. I didn't take the log to diagnose my VDI, I diagnosed my VDI because of the log.

4. The 2.3K out of the rev range is all I need to see the valves supposed activity, or lack thereof.

5. I never mentioned my butt dyno Mr. Butthurt, everything actually felt fine that night.

It just seems you are looking for a problem where their is none, IMO I would focus on why for almost 1K RPM your HP creates a negative bell curve. VDI would not cause that.

I Know there is an issue there, I'm just not sure what. The only differences are:

My lead timing dips a SMIDGE between 7,178rpm to 8,047rpm
And my separation backs down from 14' to 10.5ish

3rd gear 'dyno" starts at block 411.

Legend
Dark Blue = Maf
Yellow = Calc Load
Light Blue = Throttle Position
Orange = AFR

Attachment 197266


Looking at just the last part of the data set, all things considered it looks ok to me other than you're way to rich.

It would be easier to read if you just started the log run at 2500rpm in 3rd gear

Attachment 197267

Better question, what was your times at the 1/4 mile ?

Since when is 14.2:1 rich :dunno: You may want to go do some reading first!

How is this relevant in the slightest? Its an 8, his 1/4 mile time is crap! second its a data log, and can vary seconds thus making the time point useless. As you can see above two separate data logs and he gained 12 ft/lb of torque. thats equivalent to 25 WHP up top.

Like I stated get a dyno.

he probably meant lean lol

He would still be wrong!

That matters alot... what is his trap speed? Low trapspeed he knows what the culprit can be if it is killing his top end. IF your vdi is stuck, shouldn't you be much slower up top?

You would be surprised! Some guys have blocked off the VDI completely.

HAHahahahah ok
Lemme be more specific

I don't know where you got that single data point from :shrug: but I was looking at the WOT sections in the log file at the 411 and past

He is deep in the 11's and that is too rich in my opinion for an NA car.

It's blips up to 12 as OP mentioned as the APV and VDI opens

I'm not seeing this 14.2 ... please indicate where this is? Is it in the first log file?

The A/F in the graph of the log in your post is a 14.2:1

Attachment 197266

Ok ummm not me it looks like 11
But anyway forget my shitty graph the log file says 11.2's ish

It's hard to interpolate as well as the log is contains all the gear shifts which produce spikes and other stuff.

If you look at that file, start at row 407 to 468
This is what I was trying to analyze

Ok it's killing me, I don't even see how you can get the decimal precession out of that screen shot I posted of the AFR?
I really can't see where you are getting the 14.2 lol
The orange line is all over the place it's not held at 14.2
Sorry man I just can't see it and I'm interested in knowing how you are getting that number from that crappy screen shot

Chalk it up to color blind, Orange and yellow are identical to me.

Yes 11 is way to rich!

LOL fair enough
Cheers!