Mikes new thread :)

[mikec]

Ok hopefully this'll be my last thread on this problem

First off some background and specs

4.6 top hat turner engine,

Turner gas flowed heads.

Stripped and sent to acr to be checked over.

They also ported the heads a little.

Also out in a crower cam from v8 tuner, think the 50229.

Ms kit as supplied by nige (but not from nige)

Pwm kit, but not connected up and pipes are blocked off.

All breathers sorted now.

Running Niges "master 4.6 map"

And nb is back in now.

The main problem is a big flatspot when you boot it from idle, sometimes accompanied with a bit of a backfire through the air filter. When I say boot it, its probably idling at about 600-700 rpm then give it half throttle or so on the throttle linkage. It's that big I'd guess its not far from stalling the engine.

The other issue is the idling, its hunting around, to be honest I could cope with that, but, I'd imagine its a symptom of the same fault that is causing the above.

I've done some datalogs today of various things, which ill upload from the laptop.

In the meantime some videos pics etc.

[mikec]

Here's a vid of the flatspot and what shows up on megatune

Sorry its on YouTube, it was too big to upload here and photo bucket started playing up.

[mikec]

Here's a general vid to show pipes etc

[mikec]

And here's a vid of the flatspot again, from under the bonnet

[mikec]

hes tyhe datalos

idle4.6master.xls

fastidlemaster4.6.xls

flatspot.xls

[Hybrid_From_Hell]

OK

That doesn't sound too bad, it a combo I think of tweeking and basics that may couiple together to have things slightly off

However

600-700 for tickover is far too low, you wnat it to be I would say 800-850

having the tickover too low will cuase it to bog down, so

1. Do a timing light check and see what the tickover is giving you on Megatune vs Timing light, advise if it is out, which it may well be, a minor amount here makes quite a difference, easy way is to put a blob of tippex /white paint on the varuious markers on the crank pulley so you can see, if this has no markings 4.6 stylee, then do the spark plug / TDC settingand check wheel position

2. if you are happy that the timing is right then set tickover.

A) tighten up the acellerator cable so there is only the teenisest bit of slack in it, looks like there is a fair amount

B) Get engine warm - at least 78 degrees on MT then

C) Adjust the plenum screw watching Megatune so that you get the tickover in the 800-850 range

Then lets see how that is

Hunting is a different issue, tickover is waaay too low at the mo, one thing at a time

Nige

[Hybrid_From_Hell]

Also

Recalibrate the tps and post up the top box value and bottom box value. ...

[mikec]

datalogs

idleincreaserpm.xls

increseidleflatspot.xls

[mikec]

Ok, had an hour on it tonight

First off timing is ok, what is says on the pulley is what it says on megatune. Tdc on the pulley was checked with the engine when it was being built.

Tps values are 11 and 242.

So I went on to adjust the idle, which is where it gets tricky as its such a variation, but I've tried to get it so it averages around the mid 800's. now i am a bit concerned just how much adjusting it needed, probably 4/5 turns on that screw, seems a bit strange to me??

Datalogs above are at the new idle and the flatspot at the new idle.

Tried the flatspot again, a little better, it doesn't bog down as much but its still a huge flatspot.

Cheers mike.

[Hybrid_From_Hell]

_Hmmmm

_{I am slightly concerned that ou are having probs getting tickover up.}

_{800 is still to low, 850 would be better, can you confirm that if you wind or I should sy Over wind the screw then the tickover goes higher than 800 ?}

_{I am going to email you a new MSQ to pop into your engine to try, change nothing just let me know / post here}

_{Will do tonight or morning, need to try something ........}

_Nige

[mikec]

Is it possible to overwind the screw? Or does it just come out? I didn't wanna go to far incase something got damaged etc.

Cheers Nige

[Bull Bar Cowboy]

Seems like you really need to go back to basics to sort out this one………………..

1. Reset the mechanical base idle setting (I always used a 3 - 5 thou butterfly gap)

1. Temporarily blank off the IAC (if you have one fitted)

1. When running MS and a bucket full of idle advance on an RV8, the engine likes to idle rich in order to get a nice rhythmical stable idle…………… if it is at all lean it will hunt.

In the VE table increase the idle cell value until the engine stabilises (you can adjust the air bleed on the plenum to keep the idle rpm correct). The trick is to also increase the values of the cells that surround the idle cell by about 50 – 70 % of the amount that you used to increase the idle cell. Do this all at the same time. A happy idle speed will be 750 – 850 rpm or maybe more with that cam ……. as overlap increases so does a happy (but lumpy) idle speed !

Most folk when setting up an engine will invariably tune it lean, I guess that is because ‘lean’ feels right (but sounds wrong) whereas ‘rich’ feel s wrong (but sounds right).

Also, if you have the coolant temp sender calibration correct, your engine is running a tad cool ……….. it should be running at 80 – 85C ………… earlier 3.5/3.9’s will be 88 – 90C

[mikec]

Seems like you really need to go back to basics to sort out this one………………..

• Reset the mechanical base idle setting (I always used a 3 - 5 thou butterfly gap)

• Temporarily blank off the IAC (if you have one fitted)

• When running MS and a bucket full of idle advance on an RV8, the engine likes to idle rich in order to get a nice rhythmical stable idle…………… if it is at all lean it will hunt.

In the VE table increase the idle cell value until the engine stabilises (you can adjust the air bleed on the plenum to keep the idle rpm correct). The trick is to also increase the values of the cells that surround the idle cell by about 50 – 70 % of the amount that you used to increase the idle cell. Do this all at the same time. A happy idle speed will be 750 – 850 rpm or maybe more with that cam ……. as overlap increases so does a happy (but lumpy) idle speed !

Most folk when setting up an engine will invariably tune it lean, I guess that is because ‘lean’ feels right (but sounds wrong) whereas ‘rich’ feel s wrong (but sounds right).

Also, if you have the coolant temp sender calibration correct, your engine is running a tad cool ……….. it should be running at 80 – 85C ………… earlier 3.5/3.9’s will be 88 – 90C

Can you give a bit more detail on the mechanical base idle setting please? I'm not quite sure what you mean there.

Regards to the cooling, I went a bit ott when I fitted the engine because eventually it'll be running a log splitter, it now runs the lower temp stat, the hd snatch radiator and a fan from a p38, so it is a bit overcooled maybe.

[FridgeFreezer]

Problems round idle could be as simple as the fuel or spark maps being slightly off or the idle point of the engine not being where the idle area of the map is.

As BBC says, you need to get the corner of the map where the engine sits at idle and make sure that's right, a bit rich seems to work as BBC says - if it's lean there, or as you come away from that point, it will stumble. When tweaking this, you need to bring the cells around it up as well, if the idle area of the map is too lumpy and/or slopey the engine will hunt.

This can be affected by the accel enrichment too - by default it'll be set to work from the TPS value so that has to be working, alternatively you can switch to MAPDot which works on the MAP sensor. Accel enrichment tuning is a bit of a faff, as too rich will behave very similarly to too lean.

[Bull Bar Cowboy]

Can you give a bit more detail on the mechanical base idle setting please? I'm not quite sure what you mean there.

Regards to the cooling, I went a bit ott when I fitted the engine because eventually it'll be running a log splitter, it now runs the lower temp stat, the hd snatch radiator and a fan from a p38, so it is a bit overcooled maybe.

The ‘base idle’ mechanical setting determines the setting of the butterfly when the throttle is closed. You should be able to slide a 3 – 5 thou feeler under the butterfly in closed position. Once that setting is made you then have to make sure that it is fully open on full throttle.

With the cooling, you really need the engine normal operating temp to be over 80C. I seem to remember that the std 4.6 stat was 82C which means the engine temp will be 82 – 85C

[FridgeFreezer]

RAVE manual for P38 (4.0 / 4.6) says:

The thermostat is closed at temperatures below approximately 80 °C (176 °F). When the coolant temperature reaches between 80 to 84 °C (176 to 183 °F) the thermostat starts to open and is fully open at approximately 96 °C (204 °F). In this condition the full flow of coolant is directed through the radiator.

So looks like normal running is in the 90's.

[Bowie69]

Yup the P38s definitely ran hotter.

I've got an 82C stat in mine, a compromise

[mikec]

The base idle mechanical setting determines the setting of the butterfly when the throttle is closed. You should be able to slide a 3 5 thou feeler under the butterfly in closed position. Once that setting is made you then have to make sure that it is fully open on full throttle.

With the cooling, you really need the engine normal operating temp to be over 80C. I seem to remember that the std 4.6 stat was 82C which means the engine temp will be 82 85C

So how's that adjusted? On the throttle cable?

[ANTOINE]

Hi, I don't know if i can help you, but ,$

1 I have the same engine, 4.6l from V8 turner with T liner

2 the same camshat from v8tuner

3 head with "short ported" and induction , diy from me

4 on MS with Nigel MSQ

5 i have the PWM on

and my engine is beautifull , (to rich again because i have not working with MLV again, i wait my schorckel)

So , just to say, if you want I can send you my "map" , Nigel map for my engine, and you can try with this one .......like you want and if you want, i try to send my "map" (MSQ ? this is like you tell this I think ?) or ask to Nige if this is the same or not, and if he can send you mine

I hope my sentences are correct

[mikec]

Cheers Antoine.

I've got another map from Nige to try, hopefully tomorrow night.

But with what Nige and others has said previously, and the issue with the throttle screw, I'm sure there must be something fundamentally wrong with something on the engine itself.

I gave fridges and bbc idea of changing ve values, and although I've had reasonable results at getting a stable idle, the flat spots still there.

I'll see what niges new map does and report back.

I've also got the smaller 3.9 fan somewhere so I'll try to find that to hopefully increase the temp a bit

Cheers mike

[FridgeFreezer]

I gave fridges and bbc idea of changing ve values, and although I've had reasonable results at getting a stable idle, the flat spots still there.

One question is: which cells of the map does the engine idle in? (RPM/MAP values along the side)

Everyone's engine behaves a little differently, especially where mods or rebuilds are involved, and it's possible to find your engine is trying to idle in a different spot to the engine that was used to generate the map. Now, that could be a minor difference or it could indicate some problem (like base idle, timing, air leak, etc.)

I've also got the smaller 3.9 fan somewhere so I'll try to find that to hopefully increase the temp a bit

The size of your fan should make no difference, as it shouldn't be doing anything until the engine is getting hot. The thermostat should be regulating the engine temp (as per the RAVE quote I posted) by staying closed until its set temperature. If it's never getting to normal operating temperature you may have some cooling "oddity" (I won't say "fault", just something not plumbed as expected on a normal vehicle). If you run everything cold it's worse for it than running at the factory design temperature. Also, MS may well be staying in warmup enrichment mode which won't help in chasing down issues.

[mikec]

These are the maps before and after, I had a little play with the values as it was just a guess really, but that seemed as low as I could get it and keep the idle.

OH FORGOT TO ADD IDLE WENT UP TO ABOUT 1000rpm WITH THIS SO I TRIED ADJUSTING DOWN BUT COULD ONLY GET DOWN TO ABOUT 920 ish.

[mikec]

So I changed the values that are 52 on the second table, which were roughly the group that it idles in.

I also tried increasing the two left columns, so they went up to 71 at the top if that makes sense, as they seem to be the cells that are used when I rev it in the flatspot. But it didn't make much if any difference.

[Hybrid_From_Hell]

Idle us too low wants to be 825-near 900 minimum befire friggin about....

[mikec]

Regards the fan ill have to check and see which stat I put in now I know it was the lower one but can't remember the temp. But I did get one of each so can always shove the other in.

A quick look on megatune seemed to say cold start enrichment finished at 68 degrees I think?? Tho I may have that wrong.

I was just thinking as all this is being tried stationary having the smaller fan might help it warm up a bit.