It has begun...tuning a TR6 with Megasquirt

After about a year of ordering parts and reading lots of documentation, I finally got the TR6 running with Megasquirt and fully sequential injection. Now the fun really begins. I'm amazed at how good the idle was once it warmed up. No hunting, settled into a smooth 1100 RPM. For the initial start up, I'm using the ITB setting for fuel which is a mix of MAP sensor based engine load and throttle position sensor. I'll play around with getting a better vacuum signal from the ITB manifold, but so far it's only working so good. There's a single port at the end of the balance tube, but I also have ports on the individual runners and can try different sampling settings. There seems to be a dead spot right after cracking the throttle (AFR going lean). Once above 2500, it revs nicely with the AFR staying in a reasonable range.

The next step is to fix the slightly sticking throttle and take it for a short drive to see what the engine does under small loads. Overall, I'm pretty excited that the damn thing didn't simply blow up or refuse to start.

Let us know how it goes.....

Did u bump the compression as well?

Bump up your "acceleration enrichment" offset. It's been a while, but that and the warmup enrichment offset can take a bit of fiddling if I recall.

On decently sized ITB's the accel trigger should be pretty low, but with a cell tuned at that lower level.

Nice to see another one running MS.

I've heard that using the ITB/blended setting at first is for masochists and you should start with Alpha-N mode with barometric correction (atmospheric MAP sensor).

I've also heard that putting a fuel filter between the MAP sensor and vacuum manifold is a good way to smooth out vacuum pulses to the sensor.

GameboyRMH wrote: I've heard that using the ITB/blended setting at first is for masochists and you should start with Alpha-N mode with barometric correction (atmospheric MAP sensor). I've also heard that putting a fuel filter between the MAP sensor and vacuum manifold is a good way to smooth out vacuum pulses to the sensor.

Or a simple restrictor (think welding tip) after plumbing all of the individual cylinder vacuum signals together.

I have been through this a few times with ITBs.

1. disable all accel enrichment until your table is well tuned. Once tuned you should require very little AE.

2. The transition likely occurs at your MAP/TPS changeover point (are you still using the defualt 90kPa?). It may take some datalogs to figure out what changeover curve you should use. Megalogviewer will allow you to plot the data and find the optimal changeover points.

3. for vacuum lines: run a single line from each throat with a restrictor into a common vacuum plenum. I used an aluminum manifold port. Then run a single line to the ECU. You may also need a restrictor to this.

Are you running MS3?

Jaxmadine wrote: Did u bump the compression as well?

Compression is 10.5:1. The head has been worked, and it's running a tubular 6-to-1 header. The cam is a Richard Good GP2 cam with extra lift from the roller rockers (yes, the block was line-bored to accept cam bearings).

I decided to use a MS3 to run fully sequential injection (and eventually ignition, maybe). Plus, I like the SD card logging for autocross.

Thanks for the tips on improving the vacuum signal. I suspected the single port is simply too unrestricted. The plan was just to get it idling before doing to much experimentation. The individual vacuum ports are 10-32 thread, so about the size of a welding tip. I'm going to make a vacuum manifold with a restrictor on the output side. Worst case, I'll switch to alpha-N until I've got the vacuum signal where I want it.

Having done a stupid amount of itb tuning, I wouldnt recommend turning ae off, ever. That will make you want to throw the car in the trash quickly! Leave it on, make sure it isnt absurd and use ve analyze for the rest. It filters out accel anyway so there is no reason to take it off.

Disregard the above if your itbs are rediculously small for your displacement. ;)

I would second the notion of running vac lines from each intake runner to a vac block, then adding a welding tip in your MAP feed line to the MS. This is my IRTB Miata, and that setup has worked well for me.