Compressor Maps

[Stewart]

Keebs during this, usually all to brief, interlude into lucidity for me, I pondered mixture tune set up for initial fuel and ignition maps while driving in heavy traffic yesterday. I think this might even make sense to you sane Peugeot people!

Having started life on spanners in the 70's I find myself here trying to digitalise all the tune skills enjoyed from points and carbs and mechanical injection. Bear with me and pick the eyes out of these ideas and we might just arrive at a system to share. First of all I have been using a formula to approximate initial timing figures for different builds. It works well for initial set ups. (17.37 x stroke" )/ (Dynamic CR) + 3 deg for squish heads or 5 deg for non squish.

My engine Inlet 71 deg after tdc and static 9.5 cr gives dynamic CR 7.22 so (17.35x3.5)/7.22= 8.4 + 5 ( for non squish) =13.4 deg. It works for me.

1/ Set ignition basic curve for wot atmospheric to 13 static, 22 at 2000rpm and a max of 25 at 4000 onwards. Add 6 deg to -50kpa map max for the vac advance effect..For boost take 3 deg out for each 1 psi (15 kpa) boost pressure. ( most piston engines run around 22 deg for torque/power)

2/ Use auto tune , in my case set to TPS/RPM 12.5 across table. Auto tune from 70 or 80 deg ect and 40 to 60 deg inlet manifold temp.

3/ Since rich mixtures burn faster than lean, set up ignition map to fuel map now either on dyne or road and det can.

4/ It is now safe to retune leaner mixtures to 14.5 ( stoich) for cruise/ idle/ overrun without detonation.

5/ In the leaner areas we have set, add some advance in these areas.

One thing to add at the start here is that no engine breather venting should be allowed into the air intake during this period as any detonation or fuel tuning will contaminate the engine oil and may force oil into the inlet stream. If that happens the oil will detonate in the chamber and give us the wrong signals for our ignition parameters.

Does any of this ?????????????make sense????????????????????????

[keebs]

I think you may have lost it. All kidding aside, I do pretty much the same thing without the math. I always think of fuel injection as a carbs more sophisticated less hands on brother when making adjustments. When it comes to ignition, I used the curve for a small block chevy since it's head is similar enough for a start point. Under boost I took out 1 degree per psi which worked out pretty nice. If you have a good friend let them drive while you wear the det cans and make changes, or every time you go for a ride wear them and make the changes when you get home based on logs.

[Stewart]

I lose it too often Keebs. I think I need a long rest.........

To the progress report, it is spring here and today is dry, clear and 30 deg C. I went for the auto tune drive with the ignition set as above with af table set for 12.5 over 20% tps. It worked a treat. No bucking while fuel is tuned.It can pull off on the idle and will drive the car at 950rpm idle in 1st,2nd, and 3rd. That is torque and finely tuned, I like it!. So, to performance, pulls 6500 in third at 0.5 bar(wastegated)There is 0.5bar sitting waiting at 3000 in top gear too. Noice!

So running 9.5 static CR, 280 deg (240 at 0.050") cam , Nissan 180sx Garratt T25G, the Toyota GT4 Celica, water to air intercooler with engine coolant supplied to it, the electronic BOV, I have, 88 deg ect, 43 iat in manifold, 0,5 bar from 3000 to 6000, 0.3 bar at 6500. ( I didn't go to 6500 in top but I did in 3rd, which is a very naughty 144 kph.)

The engine fires up beautifully now using the same fuel table number as what it idles on, in the start of the table too, so thankyou Keebs, it was a revelation.....

I'm taking the win today and shall now fix the annoying gas smell and a little knocking noise in the rear, before advancing to the Det can finish.

[keebs]

Sounds pretty beefy down low. Now you've got me thinking about what 505 motor I should build. What kind of internals are you using for it to accept boost?

[Bean]

I had to google "det can" as I had no idea, so now I'm curious if you guys use the analogue copper pipe/tube/ear muff det cans, or if you do the electronic ones with a microphone to ear buds/headphones?

I'm thinking I could modify my set of mechanic stethoscopes to do the same thing which should be better than the copper pipe set up - but not sure if an electronic set would be better yet?

Rabin

[Stewart]

It had me confused too for a while Rabin. It's just a tool to listen for detonation. Logging with a knock sensor or have knock sensitive ignition is best way to go.

I was lucky enough to get an electronic stethoscope made up from an article here, http://www.autospeed.com/cms/article.html?&A=0348.

I'll be giving it a go soon.

[keebs]

I use the copper pipe method with construction style earmuffs. A diy electronic set would be nice, but you might end up having to discern between electrical noise/static and det. I've also got a det sensor wired to VEMS, I just haven't gotten around to making it active. I had a brief conversation last year with a VEMS distributor, and I believe he said it wouldn't do knock correction while either sd card logging or just logging in general. Setting up knock detection in VEMS isn't the easiest of tasks anyway, I might not even set it up.

[Stewart]

Keebs, the engine is std using different ring gaps on Hastings moly/cast iron rings. The head has been ported in the exhausts to clear out emission lumps and bumps for egr and air injection and some small amount of work went into inlet ports around the valve seat area. The pistons are std ZDJ/L which were 9.2 CR and by machining the head I raised it to 9.5CR.

Ring gaps are where I spent time researching a lot. It runs top ring at 0.056" to 0.060" per inch bore plus 0.001" and same on second ring. It hasn't got much detectable blowby. I got the ring data from JE pistons and other info.

The cam is custom billet and my spec twin valve springs. I'm running Penrite oil with zinc as well.

[keebs]

Sounds pretty straight forward, I might have to make one. Save your pennies on oil, heavy diesel oil has the same ingredients as most high end racing oils.

[Stewart]

By the way, the electronic control of the blow off valve works a treat. I fine tuned it during the week and found it quite nice to drive with. It is a bosch bypass valve from a 505 STi which was the 2.2 zdj/k engine with Bosch K injection. The Sli, 2l xn with K inj had them too. It is open to manifold pressure above the diaphragm and has a solenoid inside it to switch it on and off when vacuum is supplied. It isn't lifting off it's seat at all so perhaps something like this could help in N9T builds? I have it dialled in to open above 1500 revs and only under 0.1% tps. Over 0.1% or under 1500 was bringing it on in light acceleration or just moving off, which I could notice once I turned it off and, I then had to retune that area's mixture!

[keebs]

I've spent much time thinking about your bov setup. I like the idea, but think it needs to be taken a step further to be better than a mechanical unit. Maybe you could use dtps/dt so that the valve was triggered by a throttle decay rate rather than vac or single tps percentage.

[Stewart]

I get your point but it seems quite nice to use. The later ECU may have that function I think but mine doesn't seem to go that far. It does run a boost solenoid which I think I'll hook up again. Before this started the intent was to use what I could lay my hands on, and learn compressor maps etc. I reckon from the Garrett boost adviser app and what the engine is doing at 0.5 bar I'll go to 0.7 bar into the map sweet spot for, 240 hp and enough torque for polite acceleration..............

..

[keebs]

It was just an objective thought, hope it didn't come across wrong. I don't think any ecu's on the market have a that function, but you could give LINK a call and ask for it in the next update. That turbo looks just big enough to do what you need. She'll spin up pretty quick with a boost controller.

[Stewart]

I like to think and learn Keebs! All cool with me.

Link moved on to the G4 a few years ago so no more updates for this set up.

I'm thinking 11 psi in the manifold. Boost is at 0.5 bar at 3000 so with any luck I can get that 11 psi by 3000.

I had an idea while reading the compressor map and Garrett Boost adviser App.

How does aim for the choke line at maximum piston speed, for me or, the maximum revs for the engine sound?

I've used a boost solenoid on this before with the ecu controlling the cycle but like the fuel map it's a very varied thing to map. It does seem to make a difference though.

[keebs]

.7 bar at 24lb.min might be making more heat than power. I would opt for a slightly bigger compressor.

[Stewart]

So we are at the limit of the little T25G at 0.7 for 250 lb if we were setting up a new system? ( Not that I'm going to change it again!!)

Using the app at the choke line for max piston speed gives a minimum compressor size to my thinkin'. Does that make good thinking to you?

A small step up in size would be an ideal from there?

I'm thinking of Rabin's goals and might just see what my loony thinking comes up with. I'm thinking mid range starting 2600 and max power 5800 gives this GT2860

attachment=3450:Rabin GT2860.PNG]

attachment=3451:Rabins GT2860 and Dani.PNG]

[keebs]

The program might err on the small side to keep people sane. Size of the turbo is all about application. Do you want to drag race, road race, offroad, street? Go small for oem, tad bigger for performance, tad bigger for road course, then full retard for drag.

[Stewart]

So, how do you go about establishing a fuel map using the VEMS?

[keebs]

Well first it asks for injector size and number of cylinders, then you do a required fuel calculation so the VE table numbers are close to your actual volumetric efficiency. I used the auto tune, but accel/decel events muddied up the results too much for anything other than a starting point. It's easier to set up a log with all the important points rpm, map, tps, curr. VE, corr. VE, target afr, actual afr, accel pw, egt, spark, coolant temp, air temp. It'smore time consuming, but you get better end results.

[Stewart]

OK. So it uses a table VE and rpm to start and then you trim it to get afr. If the ignition is based on VE as well do you set up the fuel table using a base ignition map like a distributor would have for mechanical advance, where the entire ignition map has identical numbers for rpm for any VE row? I have always retuned, recammed or hot engines using a standard manufacturers advance spec and set the carb or mechanical injection afr t then fine tuned ignition off the std curve numbers. This digital fuel is so much more precise and odd to look at when you see the 3 D map how do you start the ignition graphs in the VEMS before tuning fuel during boost?

[keebs]

The fuel table is completely independent of the ignition table. Ignition is pressure vs rpm, I started with stock idle advance and simulated a distributor curve up to 3500 then just guessed. I can upload graphs if you'd like, just let me know what you want to see. I don't find carbs any less precise or complex than efi, I tuned my 550+hp 358ci v8 to idle at 14-1 cruise at 16-1 and get over 20mpg.

[Stewart]

Yes I like carbs myself, its keeping each runner hot enough to keep mixture even is my drama. What I'm interested in learning is setting up a close advance curve which is safe for detonation while auto tuning mixture ( a bit of tinkering I think I have nailed pretty well) and then using the exhaust temp and DET can or such, (after the afr is right) to fine tune ignition I'm very happy with the new T25 set up and that manifold I made. Quite flexible and it doesn't feel much less than when running the t3/4. Better set up, better tuning and better health seems to have made all the difference! The engine is going to 0.5 bar and feels like it would be on the edge of too fast, at 0.8 bar. I'll try and get a video of the thing at idle rpm in third gear. It's just fine.

With the superb digital idle air, ign and fuel control, the 280 deg cam feels smoother than the pussy emission cam the Gti's ran. I like it a lot!

Respect to you for 20 mpg out of a 500+, 350. Good work indeed!!!!! Did you use exh temp to fine tune that engine ?

Thanks for taking the time with me, Keebs and Rabin. I've spent my career working hard with Peugeots and kept up with the technology in the field but, this real,ground work is something that I have not been able to try, until recent times.

Stewart.

[keebs]

20 degrees at max rpm .5 bar scaled down 1.5 degrees per 1k rpm should be a safe starting point on just about any engine at that pressure. On boost max power is limited by det so creep up .5-1 degree at a time until you start to hear it and back off. Off boost egt and fuel consumption should get it dialed in nicely.

That 358ci was only tuned using a wideband and distributor dyno. I hear you on getting the ports to flow evenly, the biggest hurdle is getting a single carb to fuel right on a road course.

No thanks necessary Stewart. Threads like this might just open peoples minds to whats possible with a bit of tinkering.

[Bean]

Ive learned TONS sitting back and admiring the conversation, and educating myself at the same time...

I really look forward to when I have my set up in place and I'm tuning - THAT'S when this discussion will go from theory to comprehension and understanding in my mind...

Rabin

[keebs]

I smell an international challenge brewin.