SU fuel injection manifold conversion

[Tony D]

Yep, if you think about it...that single screw was enough to perform that function before you doubled it.

 

With two, you could half the velocity across the orifice and cut down on the noise.

 

Also, remember just because you have an IAC does NOT mean you don't require an idle air bypass. The IAC is NOT for idling the car! It's as you suggested: Idling it UP when an accessory comes on---base idle speed is almost always set with some sort of fixed bypass to get a base 'limp home' mode should a valve fail. The original AAR in the turbos eventually incorporated a small screw to block the pintile open so if the Diaphragm failed, the car would still idle at around 6-700 rpms. It was not dependent on a control device to function in order to start and idle the car.

 

IAC is what you use for fast idle warmup, A/C clutch engagement, even anti-stall programming and Hydrocarbon Reduction on drop-throttle--really it's a misnomer to call it an idle air controller. It's more of a "Idle Load Compensation Valve"

[Xnke]

Ok, after using a good bit of time with a radius end mill and the lathe, the whistle has been cut down a LOT. I'm now idling solely on the idle air bypass, and the throttle plates are closed at idle.

 

Now I just gotta get the intake piping made up.

[Xnke]

WOOT! O2 sensor parts will arrive on the 24th...then it's time to actually get down to business.

[Xnke]

I think I was doing better without the O2 sensor...I finally got it working so I could see my AFR's, and now I can't get a decent idle under 1000RPM. That, and my idle is bouncing around from 950-1150RPM....not cool.

 

 

Ok, Idle fixed. I watched a datalog and saw my MAP data was bouncy...lawnmower filter fixed that a little better, then I bored my throttle bypass screw ports out from 4mm to 9mm, to gain more range for setting the idle a little better.

 

It worked, and doesn't whistle as loud now as it did with the radiused port opening, so that's good too.

Edited July 1, 2010 by Xnke

[Tony D]

good to see you're making progress!

A small orifice in the vacuum tubing on the manifold side leading to the lawnmower filter will dampen the pulsations further. A carb jet from a Rochester is nice, as they are measured in thousandths of an inch, so you can correlate their size with the damping effect.

[Xnke]

Tony, you think if I send you a datalog of the car, you can tell me if what I think are pulsations are normal or an actual problem? I still can't get my MAP down to the 40's at idle, although part of that may be my ignition timing. I have not even started to play with the timing yet, although I do have my fuel maps dialed in a little better every time I drive.

 

If I had 40$ to spare right now for a piece of software that is violating the GPL, I'd buy it, just to get a good working autotune function, to get things closer than they are now. I can't really drive the car around too much, as it's not even titled. Stupid, stupid laws in KY about titling an out of state car...I've had it three and a quarter years and they STILL will not title the car, because it does not pass the state inspection. I'm probably going to get slammed with a HUGE tax just to get it titled, whenever I finally get to the point that it passes inspection.

 

 

 

Whoa, i totally forgot to ask...about what size would be a good starting point for that 'small oriface?' .023"? .035"?

Edited July 2, 2010 by Xnke

[Tony D]

If you have a wire gauge hobby drill set, using a blob of solder in the vacuum line and then drilling it out till you get a decent compromise between spikes and MAP Response to WOT is a good idea.

 

Really the idea is to keep the strong pulsations from triggering a MAP based accel loop, or affecting the enrichment circuits at all (or the higher load sections of the fuel map from being involked).

 

I mentioned a stock L28ET at 35kpa, and that's pretty good vacuum. I would say anything in the 35-40 range would be acceptable given proper valve adjustment, proper timing lead (advance), and closed T/B. It should not be 54 unless you have a big cam (or possible vacuum leaks...)

 

DanEasyguy71's 510 lift, 470 duration cam exhibited a 10" Hg idle vacuum. I'd have expected 12", but that's in the ballpark. Same goes with kPa---35 would be ideal that is where I see most of them. When we were running SU's and had the throttles cracked we could NOT get below 55 kPa no matter what we did. It was just terrible trying to work with that little resolution on the scale! But back to Dan's cam---there you are looking at 50 to 60 kPa (if my conversions are correct in my head) so you see what I'm getting at with a mostly stock engine and that kind of number.

 

You should be able to get it down there, but it may be a worn engine, valve adjustment, and yes as you mention timing advance that will affect it. What kind of 'range' do you see as a pulsation at idle? When you watch the MS table, is the little dot jumping from two or more bins? If it flicks rapidly between two adjacent bins, I'd say it's acceptable. What you don't want is a pulsation that is moving it across three bins (or more) at idle, or any place down the throttle position. I know with ITB's you can get pulsations like that well into the 25% TPS range if you have a bad situation. I'm betting as soon as you crack your throttles your MAP signal goes pretty smooth and above 1000rpms you get no pulsations whatsoever. With ITB's it can be pulsating in the 2000rpm range if it's bad. And jumping three bins then will play hell with trying to tune it!

 

Dampen it so it's not flicking more than one or two bins at idle and call it good. You shouldn't have an issue tuning idle mixture then. And off-idle you should still have a relatively decent MAP/TPS correlation without much delay to mask with an accel shot.

 

Good Luck!

[Xnke]

It is definitely not a worn engine...It hasn't got 30 hours run time on it yet, and has about four street miles. Valves are adjusted to .010 intake and .012 exhaust hot.

 

I'm jumping between one or two boxes at idle, and as soon as the throttle plates open it goes smooth. Getting idle mixture is not a problem, it is idling at 13.7-14.4 at all conditions, and idle is set at 900RPM. I'm getting an inconsistent idle now, I've noticed...I can start it up and it will run at 900RPM one start, and shut it off and four hours later start it up and it will idle at 750. Try again later, and it's 825, on and on.

 

I'm really starting to think it's my timing curve. I'm running about 17-18 degrees at 54kPa and 900RPM, I'll fiddle with the timing and see what I can come up with.

[Tony D]

Fiddle with the timing bins. If it's jumping between bins it can change and that will make your engine speed up and slow down. The timing should be the same to about 1200---take a look at the stock FSM for the lead curve to use that as an example.

 

There is no reason for it to move like that othwerwise barring vacuum leaks.

[Xnke]

ah, that makes sense. I'll make that change and see if i can get it to straighten up and fly right.

[G-rib-73-240z]

This is awsome, I came up with an idea similar to this one last friday at applebees. I started looking to see if someone has done something similar and here i am, and better idea then my idea I might add. Im glad someone is doing it so i can find out how it works out, very clean set up xnke. I might do something similar to this instead of weld in injector bungs and hope for the best. Good work, and i hope you figure out your problems and get this thing running, id love to see a video of you driving it and mashing on it. Your idle in that one video sounded cool.

 

Thomas Gribble

[74Adam]

I'm bumping this thread for two reasons:

 

1. This is a cool build and I am curious as to its progress.

 

2. I have an ulterior motive and I was specifically hoping Derek and Tony D could help. First off, Derek, where did you get that combo idle control thingy? I don't have ITB's so it doesn't matter for me but is just a clean looking piece. Ok, so I have the jeep stepper motor control body that Matt (DIY autotune) sells and now I am wondering if there is some way to incorporate a set/bleed screw into it? If you look at the photo:

 

http://www.diyautotune.com/catalog/custom-idle-air-control-body-for-use-with-jeep-40l-iac-valve-p-69.html

 

The NPT threaded hole on the left is air going out of the body and to the intake. Couldn't you drill/thread a 1/4" hole into the SIDE of that outlet and install a bleed screw with a spring? Then drill another hole into the hole you JUST drilled (say, from the top) and put a 1/4" NPT/barb into that hole? I think the body itself is big enough and obviously the threads for the bleed screw would have to be fine pitch, but wouldn't that work?

Edited April 12, 2011 by 74Adam

[Xnke]

I've been working on finishing up the rest of the car and obtaining legal status for it, so I haven't done much tuning on it. It's been painted since this was last posted, but that's about it. More seat time and datalogging will have to be done before I can call it finished.

[Derek]

I cast the block when I was doing the manifolds. Not familiar with the idle block from DIY but what your trying to accomplish is to bleed air from the filtered atmospheric air into the vacuum portion of the block.

 

Derek

[Xnke]

Well, I've been working and working and working with tuning this machine, and finally found the inconsistant idle problem...my ZX turbo junkyard fuel pump has always been pretty loud. and it's always made this WHIIIIIRRRRRRrrrrrrwhiiriiiiiirrrrrRRRRRRRRWHIIIIIIIiiiiirrrrrrr noise...And when it was doing that the fuel pressure would fluctuate with the noise level. Tuning this thing has been literally shooting a moving target!

 

Anyway, I got fed up with slipping the clutch like a madman to pull away from a stopsign smoothly, with little to no tire chirp, so I advanced the cam 4 degrees to get a little more low end...you'd initially think I'm going the wrong way but it's much more controllable now. Much more similar to driving the 300I6 fords at the office. When I did this, I started with 87 octane fuel, a new fuel pump for an 88 ford F350, and a knock-pipe-headset to set timing lead.

 

By the way...that ford fuel pump is nice and quiet, and if it can feed a 390 ford it should have no problem feeding my L28.

 

Timing lead set to 26 degrees idle to 1200RPM, then 29 1200-1600, 30 from 1600-2100, 32 at 2100-2800, 34 2800-3500, and 36 from 3500 and up. Currently not setup for vacuum advance yet, all MAP values result at the same timing for a given RPM. Engine is 9.7:1 compression ratio, and the cam is a .454" lift, 230* duration at 0.050" lift.

 

I STILL can't do better than 57KpA at idle, but it's rock solid at 57KpA. I had a little flutter in the signal, but about 4" from the manifold I installed a .030" MIG welding tip as an orifice. Probably a little small, if I had a .040 I'd try that, and then I'd likely settle on .035"...

[19762802+2]

So when do we get a driving video to hear that sweet intake sound? I have been inspired by you and Z-ya and I'm building a similar intake to use when I go Megasquirt.

Edited May 5, 2011 by 19762802+2

[Xnke]

well, right now the driver's window glass is busted out, I'm getting a new one as soon as the insurance check arrives. Too broke to buy it first and get reimbursed.

 

Next time I have a passenger who will hold the camera, we'll get a video.

[BlueStag]

Where are the TurboChargers?

[ZXT_bean]

Last night I found myself laying in bed with my mind racing, just thinking I could do the something similar. I go and google it, and bamn I find this thread lol. Well I have all the parts to build the same sort of setup. Its just nice to know someone else has done it and that its also possible. Once again, HybridZ to the rescue!

[Tony D]

"There is nothing new, only one's inability to find that which has previously been done and reapply it to your circumstances."

Dighera's Corollary to The Rubber Doughnuts Theorem of Automotive Restoration