Stock Delorean throttle bodies - why so big?

[FABombjoy]

I can see how a larger throttle body can affect the granularity of the throttle input - turning the pedal into more of an on/off switch than a linear input. Unless the TB is comically oversized I would think you could account for that in the tune

I can have MAP >= 100 anywhere from 30% to 100% TPS depending on gear/boost targets/etc. I have speed density working perfectly - alpha-n would probably break my car.

Can you post logs of the stumble when using SD?

[Spittybug]

I'm not using SD so I don't have logs of the stumble.... can you post a log and your .msq to show me what kind of VE values you have in your low RPM, higher load bins? When I was using SD I had to put in numbers >100. That's not what it should take.

I'll send admin a request to move this thread to EFI since the conversation has migrated.

[FABombjoy]

I'm on MS3 and we're plumbed differently enough that my values probably won't be useful. I've intentionally messed with the minfuel to gain more resolution in the VE table so I'm 100+ above 85 kPa.

You were seeing lean stumble?

The numbers in VE should only affect steady state operation but it sounds like you're having trouble with transient response? I would think transient issues would relate almost exclusively to accel enrichment. That's assuming the MAP sample is quality with no issues regarding sample source, tubing diameter or length, latency due to excessive smoothing, etc.

[Spittybug]

I just went out on a run for roses (y'all do remember what day it is tomorrow, right?) and captured a log. MUCH better relationship between MAP reading and throttle. I don't go to barometric until I really give it good throttle. Since my timing is tied to MAP it now behaves better, making driving even better. I have my AE threshold too high to kick in except under the hardest of acceleration, so that is next to work on. MS has me a little confused here though.... the notes say that the AE table is a percentage adder to Reqfuel yet the scale of the graph is in 'added MS'. Looking at my log, at 576.788 sec, the TPSdot goes to 114.5, over my kick in threshold. The resulting accelPW is 7 ms, which on my table is supposed to be the added amount when TPSdot is >1000. So it looks like the adder must be a percentage but is labeled wrong. That 7 ms is ~50 of ReqFuel at that VE bin I think.... 14 ReqFuel + 7 AEFuel. Confusing to get right....

What kind of % adders do you use at different TPSdot or MAPdot values? That should be fairly consistent despite our differences.

[Spittybug]

I've confirmed that my MS2e uses an absolute ms adder for AE, not a percentage of ReqFuel. The tech tip that pops up is incorrect.

I'm therefore doing some scatter graphs to look at TPSdot and PW and AFR..... lots of interesting analysis to be done with Megalogviewer.

Since you have your AE as a % adder in MS3, can you tell me what your values are? Then I can translate into ms and compare.

Thanks.

[DARCOM]

That looks fantastic, what throttle bodies are you using?

There Nissan 300zx stock throttle bodys

[FABombjoy]

I'll admit I haven't spent a lot of time here as even the stock curve worked well enough. I've enriched things just a little bit versus stock but the last session I recorded shows I could use a little more.

https://imgur.com/a/OEM4mnE

Are you running ignition control or fuel only

[FABombjoy]

After finding some free time for a few thoughts and image searching LT1 throttle bodies, I think you're seeing the effects of going to both a larger TB and a linear pulley.

The stock DMC throttle arrangement has a fairly nonlinear relationship to the pedal. I haven't measured it but I'd guess the first 10-20% of travel opens the throttle much more slowly than the remaining travel.

"Please excuse the crudity of this model": https://imgur.com/a/0y18kPr

After looking at a few LT1 TBs they appear to have a linear spool, meaning that cable travel is now directly proportional to throttle opening.

[Spittybug]

The larger body was definitely an issue that is now resolved with a slightly smaller restriction plate than what I was using. The value from the online calculator I referenced has done the trick. My throttle body has an elongated cam and another key to getting the better throttle response has been to reposition the throttle cable to follow more of the cam.

MS2e does indeed use an adder in ms for AE enhancement, not % of ReqFuel. It's also picky in what order you define the table... mine was high to low and it wasn't reading it right. That is now corrected and I add between 2ms and 7ms depending on TPSdot.

Took if for a test drive and am very pleased indeed! Very responsive. Good acceleration. Evaluating the logs shows there are a couple of lean spikes I need to massage, but overall very good AFRs in the 13 - 14 range. I'm still on alpha-n since I don't have a problem with it, but I will independently start working on a speed density tune so that I can be more consistent with what others use to make comparisons easier.

I love being able to completely change the car by just loading up different tunes. I could never go back to mechanical fueling or spark again.

The attached pics show the throttle body cam, front view, and view through the Lucite engine cover (shame to not show off the engine after all).

[DARCOM]

Looks like you have 650 cfm throttle body on there. My v8 Z28 had one. I think that's double what you need for a prv. My Nissan ones can only do 350 cfm. Im not sure what the stock Delorean throttle body flows but i know its less. If your at half throttle or less your probably at max cfm the Delorean can consume and with a restriction plate it would be like your at wide open at less than half throttle.