SBEC VNT, 89' 90', 2.2 liter, 8 valve, Attempt to reduce VNT overboost

[quantum]

Attached is a copy of a cal I've been working on to help stop the stock overboost of the VNT. It isn't perfect, but it is working pretty well. On a 48 degree day I can hold wot in 1st and 2nd without overboosting. 3rd still overboosts at wot unless you let up a bit, but it gives you time to react. This cal spools up to 10psi just about as fast as a stock VNT cal, then it climbs to ~15psi slowly. It's a work in progress, but I thought I would put it up so anyone else with a VNT that wants to give it a try can. This cal also includes a 3600 rpm stage limiter and Shellgames CE flash on knock and is set for the stock injectors and 2bar map. Let me know if you have any issues or suggestions.

Quantum

EDIT:

I put this code as an option in my Phosphate SBEC code. Download that and build as per it's instructions if you want this boost control.

[quantum]

I'll be posting up a new version this weekend I hope. I've added a few more data points to help control the boost and now have it stable at ~14psi at wot in 3rd and higher; I'm just hammering out the spool up time to keep it as fast as possible with out spiking. If anyone has had a chance to use the version up now and has something they want to see changed or added please let me know. Thanks.

[quantum]

For those who tried this; do you like the slower spool from 10 to ~15 or would you prefer it to hit the max as fast as possible? Also, what have you been seeing as your max in 1st and 2nd (every car is a bit different) and what would you like as max boost? Thanks.

[quantum]

Ok; I didn't get any feedback (not that it's supprising; really how many socketed stock VNT cars are out there) so I'm posting up what I have.

It works pretty well IMHO. I spent an hour driving with it today and I didn't hit ooverboost cut out at all, though I found that in the upper rpm's (around 4500 and higher) I still see 17psi in 3rd (My car has a high flow exhaust, so people with stock exhaust setups my not have it creep up like I do). The nice part is I don't get any part throttle overboost and if you keep a eye on what your doing you can keep it under 15 psi at a"WOT" & high rpm.

The spool up is the same as stock till ~11-12 psi and then it slows down as it heads to 15 (it doesn't take long, but you can tell the difference).

If anyone has an issue or wants changes (boost revisions, 3-bar, change the spool up, etc) please relpy and I'll see what I can do. The file contains the .bin, .tbl and .calx files. Enjoy.

[Whorse]

I might be willing to help. I have a pretty stock VNT and I want to try a socketed cal just to make sure the computer works with the socket. Once it's done I'd like to get a cal modified for about 14psi with FFV injectors.

[quantum]

I'm sure I can help. Limiting the VNT to 14 psi with out overboost shutdown is probably going to be harder than scaling for the FFV injectors (so long as you know their flow rate).

[Whorse]

I'm pretty sure they are just under +20s. I think I will manually work on controlling the VNT. I have a few tricks I want to try, and I am fully aware that it's impossible to control it precisely without a wastegate.

I am going to try and get a couple issues sorted out, socket a SBEC this week and then we'll keep in touch and try to get a nice cal tuned in!

[boost geek]

Jason does beautiful work socketing boards.

[Whorse]

Heh thanks for the free plug dick. I might head out to a local elx store and see if I can find some zif sockets to get these boards done. Really hoping to get some extra help on this.

[Whorse]

I've been running this for a week now. Stock exhaust, stock boost. Runs just like stock, except with the stage limiter which is nice. First day I thought I had a little bit of spike but that was probably just when I blew off a vacuum line to a solenoid. Since then it's been just like stock. Exhaust should still be on the way so I'll report back when that is installed.

What tables were changed by how much to affect the overboost?

[quantum]

I've been running this for a week now. Stock exhaust, stock boost. Runs just like stock, except with the stage limiter which is nice. First day I thought I had a little bit of spike but that was probably just when I blew off a vacuum line to a solenoid. Since then it's been just like stock. Exhaust should still be on the way so I'll report back when that is installed.

What tables were changed by how much to affect the overboost?

I added extra data points to the WG duity cycle V.S. boost table and made adjustments to that curve so it doesn't spike so damn hard and to help bleed off high boost better. The how much part is a bit hard to describe; I left the spool up stock, but ramped down the duity cycle after boost goal by a lot.

My over all goal was to leave the car feeling stock and avoiding the over boost VNT cars are prone to get, as well as add the stage limiter and CE flash on knock.

[Devsdaytona]

Alright, I tried this out in my car, seemed to spool up nice and smooth and everything, went to about 13pounds maximum the whole time, was a pretty cool day too.

I have no experience testing cals, so don't quote me. But I like it.

Under WOT and occasionaly under part throttle it would flash the engine light, I'm assuming its the knock ce flash which worries me.

Car is a bone stock 90 Daytona Shelby

This is the first time I have tried a cal with a staging limiter and it was pretty sweet, but apparently I need some solid motor mounts

Thank You

[Badger]

love to try this on my new VNT.....but need time to do all the PM first. Glad to see people working on VNT stuff. THANK YOU!!

[quantum]

Alright, I tried this out in my car, seemed to spool up nice and smooth and everything, went to about 13pounds maximum the whole time, was a pretty cool day too.

I have no experience testing cals, so don't quote me. But I like it.

Under WOT and occasionaly under part throttle it would flash the engine light, I'm assuming its the knock ce flash which worries me.

Car is a bone stock 90 Daytona Shelby

This is the first time I have tried a cal with a staging limiter and it was pretty sweet, but apparently I need some solid motor mounts

Thank You

I'm glad you like it. I got a little "knock" as well on my car, but I think the stock knock sensor curve was made a bit over sensitive. If you want to get rid of it; keep an eye on around what RPM you see it and then you can increase the voltage at that RPM in the KnockFromRPM table a little till it goes away. If you don't feel comfortable with that; send me the info and I can make a few adjustments and email you the adjusted file (though it may take a few tries to get it perfect).

[Devsdaytona]

I heard that other engine knocks, clicking etc can cause it to go off which is very possible with this engine. i'm gunna try driving it some more and maybe adjust that the knock curve thing.

Thank you

[Devsdaytona]

Had a good run in the car today, the ce didn't flash under WOT, the sensor is definatly being tripped a piston pin knock that the engine has at part throttle under light load.

Just though ya should know that it wasn't a cal problem.

thank you

[Whorse]

Think you could be a gent and post a cal of this with +20s and stock 2 bar map? I've run this in my car for a while and it's terrific. I'm going to be putting a 2.5" catback on the car so I'm curious how it will compare before and after.

[quantum]

Think you could be a gent and post a cal of this with +20s and stock 2 bar map? I've run this in my car for a while and it's terrific. I'm going to be putting a 2.5" catback on the car so I'm curious how it will compare before and after.

Here you go. Give this a try.

[Badger]

whats the latest on this CAL? Interested in hearing more about it!

[quantum]

whats the latest on this CAL? Interested in hearing more about it!

Nothing recent except for the +20 adjusted cal I did for Whorse.

It runs just like stock; except it tapers off at ~13 psi (like the stock cal should have) instead of over boosting. It also has a rev limiter of ~3500 when under 5 mph and CE flash on knock. If you have any questions please feel free to ask.