How to tune accel param

[Philip Lochner]

I have read every sentence and word to read on the MS sites with regard to tuning acceleration enrichments but still find myself frustrated at not getting it right.
 
Initiallly, I worked with the default figures but these proved to be WAY too high for my engine (not being of the 5.7L/350ci league I suppose). Strangely, one aspect if find particularly difficult is enrichment with only the slightest of throttle movement, just enough to be more than the MAPdot and TPS dot thresholds I've set (themselves as low as I dare go to remain above noise levels)  Also, my engine seems to buck long after I would have thought (not that "my thought are anything to go by of course..) the effect of throttle movement should have passed.
 
With so many parameters to change (I'm not complaining) has anyone perhaps a more comprehensive guideline on how to, in particular, go about tuning the accel params?
 
Thanks
Philip
MS-II/2.35/V3/MT2.25

Posted by email.

[Jim]

I'm not sure that I understand you completely .

Are you saying that you don't understand what the various numbers relate to or what the terms mean ? or something else ?

Also it would help to know as much as possible about your engine and car and any modifications that you have made .

Also does your engine seem to run well other than acceleration stumbles ? Or does it need more tuning overall ? A VE Table that is not just right can give you fits , the Ignition Advance Table also .

Do you have a Wide Band Oxygen Sensor ? This is the most valuable tuning tool you could have .

[Philip Lochner]

Are you saying that you don't understand what the various numbers relate to or what the terms mean ? or something else ? 
PL: Except for one parameter called "End Pulsewidth" (which I have no clue what it does and on which I find no explanation anywhere ...), the MT manual is very clear on what they mean and I am confident that I understand the values and the implication of the values.  I am hoping someone can advise a good PROCESS of how to go about changing these parameters. Something like this eg
1) First determine the range of both your MAP Pka/s and your TPS %/s;
2) Then change the mapDotbar and tpsDotbar values in megasquirt-ii.ini file so the vertical bars will more or less match the ranges your engine / foot generate ( I found that 200 kpa/s on the MAP bar and 50%/s on the TPS bar is what my engine (and I) generate;
3) Now set blending to 0% and try and get the best result with MAP only;
4) Now set blending to 100% and try and the the best result with TPS only;
5) Now set the blending bar somewhere in between 0% and 100% where you get the best overall result (which is currently 0% in my case);
6) Now play with the parameters (leave decel alone at this time) below the blending bar to improve things even more, to get the final result
etc etc etc
IMPORTANT: The above is NOT a reccomendation of how to go about it but it is along the lines of what I've been doing but I'm still not "there" yet.

Also it would help to know as much as possible about your engine and car and any modifications that you have made . 
PL: Again the PROCESS that I'm hoping for should be generic in nature as I'm sure this could be of value to all newbys like me, but I'll add that info to my signature 

Also does your engine seem to run well other than acceleration stumbles ? Or does it need more tuning overall ? A VE Table that is not just right can give you fits , the Ignition Advance Table also . 
PL: I'll NEVER claim that things can not be improved upon.  This is my very first attempt at doing FI on an engine.  I've set my AFR values leaning towards not leaner than 14.7 (except for very low manifold pressures < 40 kpa where the leanest is 16.5) but I do get a feel that it may still not be rich enough for this '60's technology engine - especially below 1500rpm.  I then let autotune set my VE table. At steady throttle she runs well with the WBO sensor running very close to the AFRs I set.

Do you have a Wide Band Oxygen Sensor ? This is the most valuable tuning tool you could have . 
PL: Yep, as explained above. 
 
Kind regards
Philip Lochner
MS-II/2.35/V3/MT 2.25/Innvovate LC-1/LSU4.2
Land Rover 4.6 std, 9.35CR, with moderate cam




Posted by email.

[Jim]

Please excuse Me , it sounds like you know Exactly what you are doing .

Please describe what you don't like about the way your engine runs .

If you are just trying to make sure that you are getting every last bit of performance out of your engine I can give you some general guidelines :

FIRST , make sure you have the correct Spark Plugs for your engine .
SECOND , get a .5 litre plastic bottle filled with water , preferably with a small squirt nozzle screwed on top so that you can easily regulate the flow (a finger or thumb will work) , hold your throttle at about 3000 rpm and slowly dribble water into your engine alternating back and forth between the throttle body barrels to ensure that the water gets to all cylinders evenly , regulate the flow of water so that the engine slows down to about 1500 rpm , do this until you have run at least 2 litres of water through the engine , this will blow-out any carbon build up in your combustion chambers , superheated steam is one of the few things that will loosen and disolve carbon build up . If you can get it , Chevron "Techron" gasoline additive is very effective also , but you have to add it to a full tank of gas and run out that tank before it does its job .

Assuming that your engine has a rather poor combustion chamber design you may be right in thinking that you don't want to go leaner than 14.7 , however , you won't know until you try going leaner , its not going to hurt your engine as long as you stay in the 13 to 13.5 range at kPa's above about 75 or 80 , and it can significantly improve your gas mileage .
You also need to stay in this range from idle to 12 to 1500 rpm , even at low kPa's , because of exhaust dilution of the intake charge during valve overlap , this will give you a very stable idle and may tend to allow you to back off on your Acceleration Enrichment settings .

Ignition Timing ,
for maximum idle stability you want to stay in the 10 to 20 degree range , more is better , back off if your engine knocks . Here's the test , idle along in second gear , foot off the gas , then open the throttle about half way , listen carefully for detonation , if the engine doesn't knock with 20 degrees advance then back it off about 3 degrees to be safe , you can leave it there unless you think that you may have to use lower octane gas .
By the way , it's a good idea to set you timing with the worst gas you expect you may have to use , bad gas is actually a very usefull tool for creating your Timing Table , raise every bin until you have very light detonation or knocking , this is called "Trace Ping" , then do a "Table Transform" to reduce every bin 3 to 5 degrees depending on what kind of gas you have in the tank , this can give you the perfect Advance Table for your engine .
Do not exceed the maximum advance recomended by the manufacturer by more than about 5 degrees at your engines torque peak (which should be about 3000 to 3500rpm) , as engine rpms increase you should add about 3 degrees advance for every 1000 rpm above 3000 , you may have to calculate your torque peak figure since quite often the only thing you have to go by is the timing figure at idle with the vacuum advance hose disconected and plugged , if you can then find a figure for maximum centifugal advance out of a shop manual you can add the two together to arrive at the advance you should be running at 100-kPa at your torque peak .
Keep in mind that you may not be able to get the engine to knock at low kPa's , say below 60 or 70 kPa , what you want to do here is add more and more timing to the numbers you previously have found and set in the higher kPa bins , to a maximum of about 20 degrees as the kPa bins get lower .

Example :
2500 rpm column ,
100kPa , timing was found to be best at 28 degrees ,
90-kPa add 3 degrees = 31 ,
80-kPa add 3 degrees = 34 ,
70-kPa add 3 degrees = 37 ,
60-kPa add 2 degrees = 39 ,
50-kPa add 2 degrees = 41 ,
40-kPa add 2 degrees = 43 ,
30-kPa add 2 degrees = 45 ,
etc.
etc.
Do this for each column .

This is guess work in the ranges where you can't make the engine knock , but in practice it works out very well and will make your engine very responsive and easy on gas .
In addition to this , if you decide to experiment with running your engine very lean at cruise , remember that if you go from lets say 14.7 all the way to 17 to 1 in a particular bin , you should increase your timing advance by 3 to 4 degrees in the coresponding Ignition Table bin .
This is because a leaner mixture burns slower and actually needs more advance to give you a usefull efficiancy advantage , this can be a double edged sword , leaning the mixture also creates more heat , and if your engine is on the edge of knocking it may start to knock with a lean mixture and more timing , if this happens , going that lean in that area , is not going to give you much advantage and will just make you engine run poorly . Personaly I've been able to get away with murder on my engine ,
but it has more modern "high swirl" "fast burn" combustion chambers .
It's a GM 4.3 Vortec V-6 .

After you have done all this , now you can play with your AE settings to eliminate any hesitation or stumbling when cracking the throttle open .
start out using TPS AE only .
Unless you have an oversized trottle body or a very large open plenum manifold you will probably never need MAP based AE .
Notes :
If you set decel fuel amount to less than about 80% the engine can act really strange and jerky when
running your engine at high rpm and light loads .
I inject a very short very heavy shot with zero "Accel Taper Time" and zero "End pulsewidth" , this may or may not work for your engine .
I found that I was constantly playing with my AE and couldn't get it right , until I got my VE Table really fine tuned in the areas just off idle , "auto-tune" did not do an adequate job in these areas .
Speaking of auto-tune , at best it will only get you close , you need to actually look at the numbers , all of them , by rows and by columns for any unusually large increases or decreases , or something that just plain doesn't "look" right , and fine tune it by hand .

[Philip Lochner]

Thanks Jim
 
I have not studied your reply in detail when I typed this as I will only do that tonight when I can sit and read it real slow.
 
I certainly do not (CAN not!!) know "Exactly" what I'm doing as I'm squirting and engine for the very first time - but I hope that I'm no "misinformed person" either even though I'm blond
 
Judging by the time you've taken to reply, I anticipate wonderful new insights which may prompt a flood of other questions (from others if not me!)
 
One question at this time:  I have a regular FI inlet manifold with port injection.  Is there a way of applying the water treatment in this case or is this where the "Techron" comes in?  (will have to see if we have this in South Africa...)
 
Kind regards
Philip Lochner

 

Posted by email.

[Jim]

I just assumed that a Land Rover 4.6 was a V-8 with
throttle body injection , I've never seen under the hood of one ,
there are not that many of them here in the States ,
they've gotten more popular in the last 5 years .

Is this by chance an OHC Ford V-8 used by Land Rover ?

Also if this is a Modern Port Fuel Injected engine why do you think that
it has "60s Technology" (poor combustion chamber design) ?

Some Intake Manifolds are friendly in this regard and others are terrible ,
You will have to look at yours and try to imagine how solid droplets of
water would behave flowing through your manifold .

It probably won't work , all the water will wind up in the closest
or farthest cylinder .

My mistake , I'm an old school kind of guy ,
most of what I've learned about cars came from 1970 to 1990 ,
mostly American V-8s , some BMW , VW
and 2-Stroke Dirt Bikes and Racing Karts .

The Techron is probably your best bet for a fresh clean start .
This is the only additive that BMW recomends , GM and Ford
Parts Departments carry the same chemical under different names .

The Oil Companies have alot of waste they can't get rid of , so they throw
some of it in with the automotive gasoline , then add detergents that
suposedly clean it out , this is where these deposits come from .

[Philip Lochner]

Hi Jim
 
See my replies below.
 
Remember I mentioned this parameter in MT, that I did not now know what it does, called "End Pulsewidth" (not explained in any documentation I read)?  Well, its made ALL THE DIFFERENCE.  With 2ms as default, this was WAY TO HIGH for my engine and must have been grossly over-enriching my engine towards the END of the taper time.  This is why the lurch always seemed to come so late.
 
Kind regards
Philip
MS-2/V3/2.35/MT 2.25/Innovate LC-1/LSU4.2
Land Rover 4.6 std, 4-2-1 exhaust headers, IAC
'80 Jaguar XJS V12 5.3 (10:1 CR) is waiting for its turn

Is this by chance an OHC Ford V-8 used by Land Rover ? Also if this is a Modern Port Fuel Injected engine why do you think that
it has "60s Technology" (poor combustion chamber design) ?

PL: As far as I know the original 3.5liter V8 engine was designed by Buick, intended for some sedan during the 60's, but found to be underpowered for the liking of the american public.  This is when LR bought the rights to the engine and started using it in the Series 3.   Over the years LR enlarged it to 3.9 and then to 4.6.  The cyl heads remained pretty much the same during all this time.  This is why the LR V8 cyl heads do so well with a bit of gas flowing as std they choke the engine to death

It probably won't work , all the water will wind up in the closest or farthest cylinder . 
PL: My gutfeel tells me the same but for different reasons.  There are vertical trumpets inside the plenum chamber  about 3inch tall.  I just can not see how water in droplet form will find its way through the horizontal throttle body then curve upwards and then do a U-turn to go down these trumpets.

The Techron is probably your best bet for a fresh clean start .
 PL: Is this stuff OK to be used with a NBO or a WBO in the tailpipe?  Is water OK with O2 sensors in the tail pipe?

Posted by email.

[Jim]

Ok , Now I know the engine , a small all aluminum V-8 that I think had a
displacement of about 230 cu. in. (about 3.8 Litres) , almost unheard of now .

Glad you figured out the "End Pulse Width" ,
it determines if the AE "curve" tapers to zero or tapers down to the setting
and then shuts off .

It occured to me after I went to bed that with direct port injection you can
almost get away with no AE at all , zero .

And you are right about the heads , they have very small ports and valves ,
and a very poor combustion chamber design .
I used to have an Odd Fire Buick V-6 in an old Datsun truck , I'm fairly
sure the Head design was the same as your engine , I did some extensive
porting on those heads and they still wouldn't flow .
(but it did get 33 mpg!!! and was fast even though it "sounded" slow)
If you decide to try leaning the mixture you will need more than the usual
3 to 4 degrees of additional advance , probably more like 5 to 7 degrees .
Also , since this engine has a slow burning combustion chamber it will
probably require alot of advance ,
maybe in the 36 to 38 degree range , over 2500 rpm , at 100kPa .

Maximum horsepower is at about 3800 rpm , very smooth running engine ,
Max torque is at about 2000rpm .

Water or Techron will not hurt your O2 , if anything either one will help
to clean out the small holes in the end of the O2 making it slightly
faster to respond . The O2 might stop working temporarily while
injecting alot of water .
RTV Silicone Rubber adhesives used anywhere that the fumes created
during curing can enter the intake , and leaded gas , will kill it.

Is your Jags engine still apart ?
I can give you some tricks for making the most out of that compression .
If it came with constant velocity carbs direct port injection will turn
it into a Monster .

[Philip Lochner]

I love this Rover 4.6.  It will never be (or sound.... sigh) like a big american V8 but it has a big heart.  Being so light makes up for a lot of cubic inches.  Mine has no problem pulling strongly all the way to 6k rpm without slowing the pace of pickup towards the top.
 
It has a lazy (or at least I think so) hydraulic lifter which must be addressed soon.  That's when I will do the heads (hey I do need a good excuse...).
 
The Jag is patiently waiting its turn until I feel confident enough about FI to tackle it.  I've already got the Wolf3DV4 fitted to the Jag (doing ignition only) but I'll try and flog that (good product but poor support/manual) and go with MS-2 rather.  The 26 year old Jag is in running condition.  I'm just battling to get it to retain its coolant (like an old man...)  It has port injection with EXTREMELY LOW impedance injectors (1.2Ohm) with each bank having its own butterfly. That's why I'm thinking dual O2 sensors with dual maps etc. 
 
Any / all input is highly appreciated.
 
Kind regards
Philip
MS-2/V3/2.35/MT 2.25/Innovate LC-1/LSU4.2
Land Rover 4.6 std, 4-2-1 exhaust headers, IAC
'80 Jaguar XJS V12 5.3 (10:1 CR) is waiting for its turn

 

Posted by email.

[snillet]

The rover V8 was ditched by dodge(?) before it even hit production, they were moving towards the LARGE era .

It fitted nicely into the Rover75 so it ended up there .

Nice engine though.