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Discussion Starter #1
I have a 97 NG900 SET. Although I've noticed a lot of recommendations and sites for improvements, I seldom see methods for evaluating whether too lean or too rich a fuel mixture.

Has anyone had experience adjusting the wastegate, and air/fuel ratios? Tuning the car professionally is ideally the best way to go, but I would prefer to know more.

If, for example you are upgrading to a TD04, too much boost is a concern without properly enrichening the fuel mixture.

I've been researching an inexpensive air/fuel meter to help in this regard. Prices seem vary from home made at $30.00 to over $400.00; with the oxygen sensor voltage being the primary method for testing.

If for example you are upgrading to a TD04, too much boost is a concern without properly tuning the wastegate or enrichening the fuel mixture to some degree.

I've done some research on the proper ratio, but would also like to know your opinions and ideas. What do you believe is the best air/fuel ratio on turbo'd cars?

DC
 

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12.5 - 1 AFR as a ballpark figure to work from.

The Air/Fuel ratio gauges that utilise a narrow band conventional lambda sensor will not give you a realistic indication of your AFR as they are only accurate at stochio which a turbo'd car is very rarely at. A wideband AFR meter is what you idealy require but these are a little pricey.

There are some simple formulas for working out required increases in fueling based on expected increase in airflow but obviously these do not take into account temp or if you are trying to 'dump' fuel to supress detonation. PM me if you'd like them though and I'll send you my spreadsheet.

The only way to really make sure that the AFR is correct is either to mount a wideband type sensor on the car and log the data or to run it up on a rolling road.

Hope This Helps.
Matt
 

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12.5:1 is a great afr to work on if you have water injection as this will give slightly more power
,
This is on the lean side if your using fuel alone to control combustion temps however..
12.2:1 - 11.8:1 is more suitable for reliability


Pete.
 

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Very true although I'd say 11.8 was a little too rich. I didn't make it clear in my last post but I'm not suggesting you use 12.5:1 as a daily driver AFR more a point to work from on the rollers.

Shall we say slightly either side of 12 is good for everyday use?

Matt
 

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Best Power is usually had between 12.5-13.5:1. Depending on engine design. Usually without water injection this is richened to between 10.5-11.5:1.

I know quite a few people running as lean as 13.5:1 with over 120 hp/liter to the wheels with water injection. But if you want a more conservative setup the stock Viggen runs as rich as 10:5:1.



In case the above image doesn't display, here's the link.

Obviously a factory car will be tuned much richer to remain on the safe side. A race car will be closer to 13:1 ... so you just have to decide how far you want to go, and how far is actually safe. Richening the mixture won't affect your power much, and it does add quite a bit of margin for safety. There are probably other better things to do first. Larger IC, turbocharger etc.

Best to stay conservative until the final setup is reached anyway ...

Cheers,
Dubbya
 

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I my oppinion I rather run my car rich than lean. If the engine runs lean it will lead to crazy high EGT's and knock.

Usually the easiest way to adjust mixtures is to tamper with fuel pressure. When speaking of the Trionic7 you cant get the engine to run richer by adding more fuel pressure because it will compensate the added fuel pressure relatively quickly. As time passes you will end up with equal ammount of fuel when injector open times are adjusted to work with higher fuel pressure. If someone will know more how the trionic does this, I can write it out. I'am not sure if there are differences between the T5 and T7 over this issue.

With the T5 it is easier to adjust mixtures by tampering with wastegate settings, because that is a speed density system. (controlled by boost and mainfold temp). T7 on the other hand is not controlled by those values, but rather by air mass flow (yes it works as a speed density system under some circumtances). So when boost is not a target it will vary under conditions, like outside temp, altitude, humidity aso. I would not try to adjust anyting besides base boost with the wastegate, this applies to the T7.

I run my viggen with 3.5bar fuel pressure (stock 3.0bar), but the adjustment is also made to the software.

Based on my dyno runs with upgrades I would recomend to everybody that check you mixtures before anything goes terribly wrong.
 

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I agree Vigge.
Rich is better than broken.

Water injection will always get brought up with this subject as well however. In some cases if your ECU is tuned poorly it's cheaper to buy a $450 water injection system, than to switch ECU's for roughly $700-800. Running the extra water will bring down the EGT better than the fuel would.

As for tuners who say "water doesn't burn" ... neither does any of the extra fuel beyond 14:1. And with gasoline you have to add 6 times as much to get the same cooling ... food for thought.

Cheers,
Dubbya
 

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Originally posted by Adrian W:
[qb]I agree Vigge.    
    Rich is better than broken.

Water injection will always get brought up with this subject as well however.  In some cases if your ECU is tuned poorly it's cheaper to buy a $450 water injection system, than to switch ECU's for roughly $700-800.  Running the extra water will bring down the EGT better than the fuel would.

As for tuners who say "water doesn't burn" ... neither does any of the extra fuel beyond 14:1.        And with gasoline you have to add 6 times as much to get the same cooling ... food for thought.

Cheers,
Dubbya [/qb][/b]
Water is not really an option if you live where I do, because it will freeze during the winter. Ofcourse you can built up heaters or so to keep the water from freezing, but I rather go with other opitons. One might also ask what the heck do you with extra power when roads are covered with snow and ice
 

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One might also ask what the heck do you with extra power when roads are covered with snow and ice --- Vigge

Never taken the Viggen ice skating?

Generally people in colder climates use 20-30% methanol in their WI systems. This doesn't seem to affect how it runs since nothing you put in is going to burn anyway.

Methanol is hard to come by though. In the winter you probably don't even need water injection there! But in hot summers here in Southern California I'm beginning to think it might be more of a requirement than an option.
At least if I want to go anywhere quickly ...

Cheers,
Dubbya (Dreaming of 93 octane)
 

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Originally posted by Adrian W:
[qb]Never taken the Viggen ice skating?      

[/qb][/b]
In tha matter of fact I have. Last vinter I took my viggen a couple of times to an ice track (built on top of the frozen ocean!) I will make a video this winter if weather stays so cold that driving on ice becomes possible.
I bet you cant enjoy this type of fun i cal
 

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I bet you cant enjoy this type of fun i cal -- Vigge

Rub it in why-dontcha.

There are lots of downsides to living in Southern California. Bad gas, strict emmissions, high temperatures. It's not a car enthusiast's state. Anyone wanna trade? lol On the other hand the sunrises and sunsets are gorgeous!

Sunrise From My Roof

Sunset Out My Window

Guess there's a silver lining every now and again. Sure is pretty, 'least whenever we get a break from the smog.


Cheers,
Dubbya
 

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Originally posted by Adrian W:
[qb]Anyone wanna trade?  lol [/qb][/b]
Hi,

I want to trade!!! I live in a country where it is cold most of the time. I hate it when it is dark during day time! I drive a convertible because I love the sun! And I don´t mind if I lose a few horses in hot weather - my Viggen performed perfectly at nearly 40 Celsius on the Ring this summer.

Sadly, I studied the wrong subject for moving abroad (I studied law, and German law is much different from American law, so I wouldn´t be able to make a living from this in the US). So I will have to stay here in cold old Germany till I´m rich enough to move to your neighbourhood

BTW, I´m back from my ski-trip, and it was great

Yours,

Philip
 

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BTW, I´m back from my ski-trip, and it was great -- Phillip

Sounds like a blast! We actually have pretty decent skiing here in the winter as well. Lots of big mountains nearby. In fact there was snow just a few days ago.


I wonder how the MapTun and speedparts upgrades deal with A/F ratios for hot and cold weather, hmmm ....

Cheers,
Dubbya
 

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Although I haven't had Fredriks' software on a dyno, yet, I would take an educated guess and say that it runs on the rich side - judging from my mileage figures. I've got the 'Green Giants' and a larger intercooler but I'm sure Fredrik took those into account when he did the fuel mappings. My previous software was done by a few fellows that worked at the engine development lab - it was a much milder version of what I'm now running. It dynoed 230 whp and 295 ft-lbs of torque. The A/F, at its' richest, was 12.5:1. It was very nice software and actually improved my gas mileage. With Fredrik's software my mileage has decreased but the
coefficient has more than compensated
 

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Sounds awesome! I'd love to see a dyno sheet and see what sorta shape it was. Sounds smashing. My A/F ratio stays around 12.5:1-13.1 as long as I keep the RPM below 3000. The higher the RPM on a stock Viggen, the richer it runs ... or I should say, the more airflow the engine takes in the richer it runs. (dyno 1,2 dyno 1,2,3) My richest A/F ratio is right smack at my peak hp. Pretty clever tuning if you ask me. Especially considering that at my peak hp of 213 whp I'm only running about 13.5 psi of boost, and going as rich as 10.5:1. (On the 213 whp run it got as lean as 10.9:1 or so. Each run was progressively leaner.) Somehow it still manages power. No complaints here.

Cheers,
Dubbya
 

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Discussion Starter #16
The lean mixture is most likely caused from the heat expansion of the air flow. As you perform more runs...the boost gets hotter; the air/fuel mixture runs leaner due to heat expansion, causing less fuel to occupy the same space.

DC
 

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Discussion Starter #17
forgot to add...

your ECU would typically compensate upon running higher boost, by richening the air/fuel ratio..or dumping more fuel to prevent detonation...at peak boost.

Hence my original inquiry on measurement of exhaust gas temperature. There is a more direct correlation but consistency to the temperature on higher boost levels, which in essence begins to lean the mixture at peak hp/torque.

At what level of boost or EGT due you start to consider larger injectors, and fuel regulator...? Of course Viggen owners, expecially those that have late model types have the sophisticated ECU setups, and fuel systems already. However for those of us that have the earlier NG900's, mine being a 97, I am concerned about overboosting the car going into a stage 4 setup.

DC
 

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The lean mixture is most likely caused from the heat expansion of the air flow. As you perform more runs...the boost gets hotter; the air/fuel mixture runs leaner due to heat expansion, causing less fuel to occupy the same space. -- DC_Saab

I wouldn't imagine this is the case. All Saabs compensate for temperature when calculating the fueling. T5 uses a temp sensor, T7 uses a temp sensor, and uses an AMM which automatically does it anyway.

As for the EGT, most Saab tuners appear to try and keep it below 1700-1750 degrees F, or about 900-950 degrees C.

Saabs are pretty resilient when it comes to EGTs when compared to most turbo cars. The B235R has the added advantage of the Nimonic exhaust valves. Brad from KC Saab has gone as high as 2000 degrees F on his Viggen without incurring damage!
Though he generally keeps it around 1750. He uses water injection to keep his EGT down. When he ran 2000 degrees his a/f ratio was 14:1, he was under considerable boost, and because of the water injection he still did not detonate.

Also too much ignition retard causes higher EGT's because the fuel mixture has less time to burn before the exhaust valve is opened. So if you can adjust timing, as long as you can avoid detonation, more advance is helpfull. (As long as you also don't go past MBT.)

Tuners are still reluctant to use water injection however, presumably for a reason.

Summary: Keep it below 1700 to be safe, 1750 is still ok, but might want to keep a closer eye on it.

Cheers,
Dubbya
 

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Discussion Starter #19
Adrian

I thought 1600 was a pretty high number for Turbo'd cars, as I'm considering a gauge pod setup, to show the EGT.

But I understood that 1500 and below was average for most stock turbo'd Saabs. While modified Saabs have the potential for running 1600 + , with detonation a problem. Was 2000 normal or just before the engine detonated itself? What is the name of the guage you've seen these high temperatures you suggested earlier?

I've also considered water cooling, but something about having to rely on knowing if I have enough water before I played around or ran hard bothered me. I would prefer not having to rely on it but only use it as an added feature when really necessary. If I could tune the car air/cooled with safe temperatures for the power I want, then I would consider water cooled as an option.



DC
 

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I do not beleive EGT is the bottom line. Each engine has a prefered EGT because of engine deisgn. I play with SAAB's my target is 1750F I have run as much as 2000F with out detonation(12.5 a/f) Saabs have knock sensors to check for detonation. The timing was advanced 5 degrees to lower EGT to about 1800F (12.5 a/f)
The car runs ample amounts of water, 1mm jet with 100psi mantained.
The car have even run 14.0 a/f with out detonation. These are very tough engines, great for learning things.
I would not be have a problem tring 1700F with the correct amout of water if the head did not come from retared igntion timing. -- Brad from KC Saab on this link.

There's where I got the info. Granted it's a Viggen, which is a little more tolerant of ETG's, but Chrysler and other single exhaust valve cars are more sensitive because they only have one exhast stem to transfer the heat through. The two exhaust valve heads trasnfer the heat away through two exhaust valves, and in the case of the Viggen this is through a highly conductive Nimonic alloy, which also has a high menlting point. In older Saabs Sodium was used to fill the valves, and increase their cooling capability. Hope this is helpfull.

Cheers,
Dubbya

edit: The reason I refer to single exhaust valve cars is that the person Brad was talking to had a turbo 8 valve Chrysler 2.2. So his reference to 1700 was to him. On Saabs this should not be pushing anything. I'm also told tuners like Hirsch use about 1700-1750 as a reference.
 
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