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Tuning for cruising and the spark map....


V8 Freak

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Wow.. Thanks for the great feedback.

I took the truck for a drive with TunerStudio running tuning while I eased it through the new map. Actually performed pretty well and I managed to hit a lot of the map cells.

Couple of things I noticed:

- I never managed to get above 95KPA

- Gentle acceleration in low gears was hitting the "cruise" area a number of times.

I've changed the map hoping to interperate your comments above. I've not dropped lower at the low revs as this gives me a good situation for lanes / crawling and quite stable tickover (Although that's probably more down the the idle valve..)

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Should I remove 100KPA, use 95 as my ceiling and introduce myself a 65KPA row to give a little more adapatability in the cruise area?

(Or should I really be able to hit 100 and what might be the cause of failing to be able to do so at the moment?)

Awaiting any further suggestions.

Neil

(I've not run this map yet)

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If you are not hitting 100KPa then it could be that the airbox/filter is restricting things a little, I manage 98/99KPa, but blame that on the snorkel.

Of course the other thing is a small variation in the MAP sensor, and not worry about it. As long as you tune to the signals received it should all work OK :)

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Best to check your TDC with a dial gauge or manometer to ensure it is correct ……… but even with all the hype, I have never found one to be out on a RV8. I am led to believe it is the very early 3.5 engines that could be amiss in this area.

Although running the engine a fair bit lean will increase the MPG (on mine I got about another 2-3 MPG overall on a run), it will also increase the engine temp and localised hot spot temperatures due to the lean mixture leaving hot unused oxygen as a result of the combustion process. These hot oxygen atoms will chemically mix (adhere to) with the Aluminium atoms to create further heat………… see here as an example http://www.iap.tuwie...lery/adsorption.

I would go for a max lean of 16.5:1 (only in the cruise area) and then increase the timing by 5 – 8 degrees (maybe 10 at a push). You might need to play with the timing in surrounding cells so as not to cause pre-ignition when you hit the gas.

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Hi Ian...

Thanks for the feedback. I think I'll simplify the KPA scale to give me two more rows so I can have cells surrounding the cruise area as you suggest.

I'll do some doodling later and post up a suggestion before going out and burning holes in my pistons !! :)

Good to see you back.

Neil

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Neil

Hills and Dips can make the difference between hitting 100 KPA foot down or not.

Its one of the reasons I have all my MSQs set at 97 / 98 - on the basis when you wnat full chat you wnat it all,

and being top or bottom pf a hill is not something to have to think about !

Just back from 4 Hours TIG Course so feeling brain dead ( :P ) but some info

I am rather concerned you have popped 30+ Degrees advance in the cruise section - apart from the fact not all V8s can take

the same max advance or spark avance curve, 30+ in crusiing stands a huge chance of problems.

Max advance and Spark curve aside, a few bits to try and help

Dizzys have an advance to give economy when crusing, as the KPA will drop at part throttle, making bobs weights come back in, and lower the advance from

WOT (Fully Flung Outwards) but will still at mid KPA give advance over WOT max advance. Racing engine often have no vacuum at all, and just run max advance vs RPM,

fine for power, applaing for Economy !. But economy is geared via a number of key things.

These are

KPA and RPM - these you have identified via the crusing cells so "Tick"

AFR

Spark advance

OK AFR

Afr is leaned off to give better fuelling, without getting to tech, the fuelling is leaned off as the BHP drops as it is a crusing cell(s) on modrn ECU these can be very lean

indeed, and in the case of 4.6 V8 as I have mentioned before the leaning off was too much for some engines, as they will run "Core heat" esp if "locked" into the lean cells

for extended periods. The heat build up on a lean engine will give piston crown local hot spots (can burn a hole in the piston) and also bore heat , again localized

and often the cause of liner problems, it is a "Different" heat to the coolant heat ./ Temp, ie you can have two very different heat level, the coolant and then a vast

amount of degrees higher the piston crowns / bore, such is the localisation that the heat doesn't bring the coolant up to its level - its dangerous not onlydue to the high

temps, but the fact is is so local, can jump high vvv quickly can do irrepareable damage and often you will not know

Spark / Advance

Running more advance at lower KPAs is fine, is what a vacuum unit does on a dizzy, but there are limits and I think you are way in excess of thm - the reason is the

greater avance again geneartes heat levels just as above, but couple this with a leaner burn and things get nastier faster

Too much advance cuases detonation, pinking as most call it, this actaully is lower torque and power outputs than at lower degrees etc but I digress, pinking / detonation

is a warning that your engine is over spaked and damage can quickly occur, spark advance too high AND leaner = 2 x as fast. At WOT detonation can be heard (not always)

at crusing, it won't. On modern systems this is controlled by a knock sensor backing off the over advancement off the table, all well and dandy till th knock sensor fails, better

system go in limp mode, so destroy the engine.

I would honesty say that the fuel savings on a milding tuned 4.6 such as yours via cruising tweaks will be minimal even when / if you are spot on,

but the risks you are running are I have to say "High". Most of the spark maps I have done are rolling road based, sorted via proper systems, however these are power

based and not economy based, I would suggest a MILD addition to the cels, (and not a set number across the block of cells as the step up down will be more like a smack on and

off the head vs a smoth ride - ie if speed / rpm / KPA puts you at the mid point of 2 cells with vast changes it can be an interesting setting !

MILD Spark tweak, graduated, and maybe AFR tweaked similaly a BIT, but without a knock sensor you are frankly on the edge sir :D

Hope this helps,

Nige

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Ok.. So we have some different views in the thread.

Using Ian's recommendations I played around and built the attached, but readig your post Nige, you advise caution.

Ian has suggested numbers that I have read but constructed a "wuss" version aiming slightly lower than his recommendations for a start point.

Perhas you could make some suggestions or comment on the attached Nige.

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As ever, posts and suggestions from others, especially Ian and AncientGeek are welcome.

I'll be following up the knock pointers above when I have a few moments to spare. If there is a way then maybe it should be explored and maybe of benefit to other forum users.

Regards and thanks in advance.

Neil

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70 KPA is too high a KPA for those sorts of avance imho

Also as KPA drops advance can increase, you have a mix there ie

70 KPA 18 35 34 34 35 26

65 KPA 18 35 35 35 33 26

ie 70 KPA cell 35 has then a LOWER advance at 65 KPA of 33 ???

I still do not like this at all but if you wnat to try :

70 KPA 18 24 28 30 28 26

65 KPA 18 26 30 32 30 27

Personally I think you should stop and sort out knock sensors, this way you can tell whats going on

This is natty : http://www.viatrack.ca/

Also worth looking at a EGT as this will give you a better idea of piston head / liner heat issues

I will have a lookie, I have another order coming up so I can add some bits in and we can sort this idea out 'properly' vs the Oooer Pop Bang bugger :( stylee :D

Nige

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Nige is right about the 70KPa thing, I think its consequence of your gearing. Perhaps a series of gradual changes to see if you can get your KPa at cruise down a bit. The 45 degreees I was talkling about was at 50KPa. My cruise KPa has come down a lot after staring at maps and feeling the Force flow through me.

Also he is right about the sudden change in spark advance. What happens if you are in the transition zone slight changes in MAP and rpm cause wild changes in advance.

I think it would be difficult to get pinking at an easy cruise but I don't want to be accused of causing melted pistons. I'm a bit more gung ho about advance at cruise whereas I'm more cautious at WOT. I think that Nige's maps are too advanced at WOT above 3000 rpm and there is one map posted in the main thread (not his) that is positively dangerous. But I run at about 13.5:1 at WOT whereas I would guess Nige is running much richer. A richer mixture is less likely to pink.

Talking of AFR's, I think you should go a bit richer at WOT. You can also go a lot leaner in the decel zone, above 1500rpm and below 35 KPa.

Let the Force guide you.

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Idle vacuum and cruise vacuum is more a function of engine design and to a certain extent engine tune. However, I would like to see your cruise kPa similar to the idle kPa ………… so 45 – 60 (55 – 60 probably ideal) is the sort of numbers to be looking at.

At cruise the engine will be tickling along at minimum effort, that is why you can afford to lean the mixture and increase spark. The idea of throwing in some more spark advance, is to increase the efficiency with a low throttle opening ……… so effectively starting the combustion process at the right point (so maximum cylinder pressure occurs at exactly or very fractionally after TDC) is vitally important to the fuel economy ……….. more bang per buck so to speak………..

However, don’t expect large gains from what could be a very long winded and frustrating tuning process …………….. 4.6L powering 2T+ with the aerodynamics of a brick out house is never going to produce an economic result !

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Reading through the responses I took the 110 for a sub zero drive after changing the thermostat also in sub zero temperatures.... Very cold hands but now running at 88 and stable.. :)

I spread the map out KPA / Revs so I could see the cells it was hitting clearly but largely left it unchanged.

You are all right...

The gearing means that cruise at 60 MPH is at 1800 RPM, but 75 - 80 KPA typically, wind and incline dependant.

On slight downhill areas where I'm not on overrun, it's down at 70 - 65 KPA.

Only in 45 - 60 KPA area on runs down reasonable hills where I don't want to slow down and keep a touch on the throttle.

As this will be a small amount of the typical life on the road, I'm inclined to move the 1600 - 2000 / 45 - 60 KPA cells to about 28 - 30 degrees and lean to about 15.5 AFR and not try for much more.

Any more suggestions before I set about building a map tomorrow and trolling off for a run ?

I'm keen to see if there is anything we can try in knock terms just to help refine spark maps without having dyno / rolling road sessions and as it will just help to look after the engine if fuel is contaminated or I'm up some mountain polluting the quiet environment with some V8 sounds.

So if there is something we can try over the next few years while your Vapour build carrys on Nige.... :blush:

Neil

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