1994 Nissan Sentra SE-R going VEMS, then turbo.

[BenFenner]

I'm new here, so this will be my introduction, and hopefully a good explanation of my car/project. I'll try to keep it up to date as others have done.

So, here is my car:



It is a USDM 1994 Nissan Sentra SE-R. I've taken the modification road that I think most people recommend, but rarely follow.

I upgraded brakes first:

Front:




Rear:








Needed new wheels to clear the brakes, so they went on too:



I then moved to suspension, installing 3-way adjustable sway bars, rear tower brace, and I have stiffer spring/dampers on the way. (Sorry, no good pictures.)

The battery moved to the trunk in anticipation of turbo, and for better weight distribution:



Notice external cut-off switch:




Now I'm finally on to the power (it's been four years since I started, continually being plagued by money issues). The money problem is no more, so it is time for a turbocharger. For those of you not familiar with these cars, the SE-R model came with the USDM SR20DE motor (also used in the USDM Infiniti G20). This is the detuned N/A version of the beloved SR20DET motor everyone is so keen on. After scratching the idea of turbo-ing my motor, I've decided to drop in a JDM SR20DET, trying to keep the cost and hassle down to a minimum. This is where VEMS comes in. I've decided against the typical JWT ECU. It would be a good choice, but I want to learn engine management, and I'm taking this chance to do just that.

EDIT Sep, 2007: I found out my stock motor is good for 350-400 HP on stock internals, so I've decided to just turbo my stock motor instead of doing a motor swap and take advantage of the better off-boost throttle response from the higher compression ratio (9.5:1 vs. 8.5:1).

The plan is to equip my N/A car with VEMS, get it working to stock or better performance, economy, etc. and learn what I have to learn about tuning an N/A motor. I will then drop in the turbo motor, and be in a good position to extract the amount of power that I'm looking for with general ease.

I've done my homework, and it seems I have two or possibly three major questions right now.

What do I have to do to buy VEMS, and whom/where should I buy it from?

What do I need to do about the Nissan trigger situation, and where can I get a machined cam angle sensor disc? (Should I do a crank angle sensor as well?)

Where do I get one of those wonderful VEMS to Nissan factory harness adapters I've seen pictures of, and which one will work with the car with the least re-wiring?


Let the party begin,

-Ben Fenner


Edit: If you're reading this for the first time, and don't want to wade through a whole ton of technical, Nissan specific craziness skip to page 8 where it gets more interesting.

[BenFenner]

Here is some more information about my plan of action:

I plan on working with the stock ignition (distributor) at first, getting that to work to learn how that is done, and to introduce as little new variables as possible. I'll then upgrade to coil-on-plug, or what ever the prevailing trend is, and do a sequential, non-wasted spark ignition set-up.

I'm not worried about sequential fuel delivery, semi-sequential or what ever is fine with me.

[BenFenner]

I've been conversing with Rob ([email protected]) over e-mails, and he wants information about the USDM SR20DE wiring harness I'm using so he can decide which one of his harnesses would be best for me. Here is the info I have from my factory service manual. If there's anything else you need Rob, just ask. If you'd like, you could send me the pin information for your harnesses, and maybe I could do all the work, figuring out which one of yours would be best for me. Either way, here are the pictures:

ECU Harness Connector Terminal Layout


ECU Harness Connector Terminal Layout Explanation Page 1


ECU Harness Connector Terminal Layout Explanation Page 2


ECU Harness Connector Terminal Layout Explanation Page 3


ECU Diagram (condensed)   [It might be a good idea to download this picture and rotate it for ease of reading.]


ECU Diagram (full)   [It might be a good idea to download this picture and rotate it for ease of reading.]

[BenFenner]

Rob and I have also been talking about CAS trigger discs. We need to find out which one my engine has. Here is the picture from the FSM:



I will take the thing apart sometime soon, and get you good pictures and measurements. I just don't have a timing light right now to put the car back to normal when I'm done... =/
So, keep an eye out for those pictures soon.

[[email protected]]

You shouldn't need to remove the crank angle sensor, just pulling the cap off and removing the covering plate should show you the disk.

From the D-shaped centre I'm guessing that its the same as the black top SR20 CAS disk:


If so, you can use that disk.

That is a 64 pin Nissan connector which I have in stock.

The problems you will encounter are: Air con, we dont have the facility to control it, as I understand things the ECU takes the aircon switch in to activate a higher idle, and it takes in the dual pressure switch to cut the aircon off when you got to WOT.  As we have smart predictive idle we dont have the facility to control this, so you'd need to look at ways of driving this if you're so interested.

You should be able to use the Dual fans using the waterpump trigger to activate the second set, although these may be activated by the ECU for air con...

Finally I've never seen that particular way of firing the coil, it has the igniter built in it seems so controlling that will be easy enough as Its a case of controlling the transistor base in the usual way, it's the function of the resistor that is of primary concern - I know that some distributor systems monitor the coil for misfires, so it may be that but we need to know its documented function to be sure.

[BenFenner]

Yah, I was thinking I would have to remove the entire distributor unit from the engine. Obviously that is not the case now that you mention it. I'll be able to get pictures of the CAS disc very easily then. Watch for them soon.

As for the air conditioning... I completely removed mine during the installation of my third replacement engine (long stories) so that isn't a problem for me. My friend who's installing VEMS on his BMW e30 has A/C though, so he'll have to figure that out.

That's good to hear about the fan control. Water pump trigger. Got it.

About that resistor in the ignition circuit. I think I know which one you're talking about. It is connected to pin-3, correct? I will see what I can find out about it in the FSM.

[BenFenner]

I've looked all through the FSM and I can't find a better description of that resistor. I will post a question to the SE-R mailing list, and possibly message board to try to figure it out. I'm going to go take pictures of the CAS disc right now.

[BenFenner]

Rob, you said I have the 64 pin Nissan ECU harness. You sure it's not 66 pins? I counted from left to right, and got 33 for the top. Did you scroll the pictures left and right to see all of it? The forum format is cutting off part of the picture, with a scroll bar at the bottom. I wasn't sure if that threw you off.

[[email protected]]

The connector I'm thinking of has
8 wide (high current) pins
gap
7 pins
threaded connector
8 pins
gap
9 pins

[BenFenner]

Yep, that's the same one I have. I must have counted wrong. Stupid me.

I'll have those CAS disc pictures here soon, once the web site I use to host pictures gets its act back together... =/
If you don't see 11 pictures in the post below, the connection to the server is being slow, and you might have to wait a couple hours for it to work itself out. It doesn't normally have these problems though, so it shouldn't be a regular issue.

[BenFenner]

Here are the pics I took of the CAS disc in my car. I measured it at exactly 54 mm in diameter. I didn't really meassure the distances to the slots, or the holes. Sorry. From the looks of it, the black-top SR20 disc you mentioned before should work. I'll just have to drill two holes in it to make it work. Correct?
























I'm still waiting to find out about that resistor. If I can't figure out what it's for, can we just pretend it doesn't exist? What would be the plan of action?

Oh, and apologies go out to any non-broad band users... =P

[[email protected]]

Hmm,
That looks to be the same as the Pulsar GTiR distributor type.

With this type it is possible to use a simple trigger which will drive a single coil using the distributor and batched firing.  Which is not really what you're after.

It might be possible to put holes in the trigger disk and mount it that way, but I'll need to check the size of the disks tonight.

[BenFenner]

Just to be clear; this is the resistor we're talking about, right?

[[email protected]]

Yes thats the resistor.

Bad news on the disk front, the SX ones are 50mm (~2")

Is there likely to be a demand for these disks?

[BenFenner]

I wish I could say the US SR20 crowd has caught on to the stand-alone engine management scene, but they all seem to be satisfied with either the JWT offerings (pre-programmed ECUs) or stock turbo ECUs with piggy-back fuel/ignition/boost control. I could always swap on a different distributor like you mentioned before, and I could even skip a step, and go to coil-on-plug immediately. I still need the cam angle sensor data though. Which distributor would you recommend? Or what should I do?

I could always design my own disc and have www.emachineshop.com make one for me, or see if I can get my university machine shop to let me make one, or have them make it themselves. I'm not a stranger to a machine shop. This is an option as well.