3.5 vs 3.9

[Bull Bar Cowboy]

The increase is a lot less than 20% …… in the case quoted its 17% but also higher in the rev range……….

I am not surprised that you come up with other numbers that are really just variations on a theme ……………. Different markets have differing requirements and therefore the specs will all be slightly different …………..I guess you are going to find a lot of 4.6 NA spec engines on the UK market ?

Here are the P38a UK specs ………….. note however, the 4.0 litre is not the 3.9 that I specified in the above post. The later (post 94) 4.0 litre is a different engine and more akin to the 4.6 in that it has cross bolted mains, a serp front cover, and a different cam. The 3.9 I am referring to is from the RR classic 90 -94

If you want to talk massive and huge then perhaps we should make a mention of the 6.2L Merc AMG V8 ………….362 Ft/lbs @ 2000 rpm and 405 ft/lbs @2600 rpm …………this would be good for our applications but these motors are scarce to say the least

Or the stroked Big Bock Chevvy that comes out at 9.3L (square engine …. 4.5in bore and 4.5 in stroke) ……… this produces 1500 bhp when normally aspirated, but unfortunately the torque figures are not to hand ………….. that motor carries a serious weight penalty !

With regard to your comment s of EFI Vs Carbs …………. An RTV trial is not exactly off road driving as I see it with regard to silly angles etc ………… more like a Sunday afternoon stroll…………..each to their own ............

Ian

[Bull Bar Cowboy]

mmm diese....................

ah sodit

Shouldn't you be asleep at your desk this time of the day.........

Ian

[300bhp/ton]

First off quite with the friggging ...... every where

The increase is a lot less than 20% …… in the case quoted its 17% but also higher in the rev range……….

I am not surprised that you come up with other numbers that are really just variations on a theme ……………. Different markets have differing requirements and therefore the specs will all be slightly different …………..I guess you are going to find a lot of 4.6 NA spec engines on the UK market ?

So are there lots of technically differences on the North American spec 4.6??

Come on it's still a 4.6 and the nummbers could easily be reproduced on a UK spec 4.6 and in either case it would be massivly out performing the 3.9 at the same rpms.

If you want to talk massive and huge then perhaps we should make a mention of the 6.2L Merc AMG V8 ………….362 Ft/lbs @ 2000 rpm and 405 ft/lbs @2600 rpm …………this would be good for our applications but these motors are scarce to say the least

Good for our applications??

Damn stopping the drivetrain breaking with a stock TDI can be a challenge let a lone a spohsiticated 6.2 V8.

Or the stroked Big Bock Chevvy that comes out at 9.3L (square engine …. 4.5in bore and 4.5 in stroke) ……… this produces 1500 bhp when normally aspirated, but unfortunately the torque figures are not to hand ………….. that motor carries a serious weight penalty !

Ok so lets try and stay on topic shall we, lol

With regard to your comment s of EFI Vs Carbs …………. An RTV trial is not exactly off road driving as I see it with regard to silly angles etc ………… more like a Sunday afternoon stroll…………..each to their own ............

Ian

Well I geuss it depends on you idea of RTV trial, what we do is certainly more extreme than ANY trail you're encounter in the UK.

Here's some pics from my local club:

I admit angles never look as impressive in photo's but trust me the angles are more than sufficent enough.

BTW - the 3 vehicles pictured are all carb, stock 2.25, factory 3.5 V8 90 with twin SU's and the Rangie runs a 4 barrel.

[dollythelw]

Shouldn't you be asleep at your desk this time of the day.........

Ian

I am

Im sure I saw a 4 barrel webber at Merc Performance Engines the other day - I tell you kids, its the future!!

[FridgeFreezer]

Well I know it can be done, but to go from a twin SU carb setup to EFI is a lot more complex than that and a lot more expensive. How about heads for injectors, the injectors themselves and all the other gumf that’s required not too mention the wiring. The carb was a simple bolt on operation that took half day or less to fit.

Last Sodbury I bought three EFi setups complete apart from the ECU and AFM - inlet manifold, injectors, loom, the lot. I paid between £5 and £20 for each. You need a HP fuel pump (woo). The heads are the same save for a tiny notch where the injector sprays, you can live without it or you can add it with a dremel and a vacuum cleaner while you swap the inlet manifolds...

The sum total of wiring to join it to the rest of the car is about 5 wires - ignition live, fuel pump, coil, and ground.

Complex is in the eye of the beholder, but you can tune SU carbs on the driveway with a few hand tools, you need tuning software and PC for proper tuning of any EFI setup, or a hand held tuner if ones available.

My tuning laptop (a toughbook no less) cost me £25 off eBay, the tuning software is free to download (and open source) and there's an "auto tune" feature that tweaks the fuel map to a target mixture as you drive. In fact if you fit a wideband O2 sensor you just give the ECU an AFR target map and it constantly tunes itself to hit it to a very high accuracy.

Take a look at the New Defender thread, they comment that the car seems to keep accelerating after you take your foot off the pedal, the TD5 was they same and this is consistent with many other ECU controlled setups.

I don't think you can use modern diesels as an argument in a discussion about petrols, my van does the same thing as it's totally fly-by-wire and the ECU is programmed to act as a buffer between the nasty harsh demands of the driver stamping on pedals and the nice smooth gentle responses that are best for the engine and any passing dolphins or pandas. Quite frankly you may as well glue the accelerator to the floor and drive with the other two pedals there's so much lag on the bloody thing

But for some reason I think (well read and hear often) in the UK carbs seem to be viewed as old school and inferior which for want of another word is total bollox, lol

Which is why all the new cars sold these days run carbs - why the F1 boys are tripping over themselves to fit carbs I hear

You might find this article interesting, here’s an extract:

So an aftermarket race carb versus an out-of-the-box factory ECU? Good test...

Edited to add: Am it picture tiem?

OK lets play:

You're right, it never looks as steep in photos does it?

[Astro_Al]

First off quite with the friggging ...... every where

43% of the words in your correction contain errors...

...

...

...

[Bull Bar Cowboy]

Well I geuss it depends on you idea of RTV trial, what we do is certainly more extreme than ANY trail you're encounter in the UK.

Who said anything about trails ? ................. try sitting on a 60 degree plus slope at an angle of 35-40 degrees whilst your winch monkey rigs .......... then see if your carb will allow the engine to tick over ......never mind giving the correct AFR if you punch the gas pedal..............

As for adjusting your SU's on the driveway with the minimum amount of tools ................ thats a bit like setting the torque on a cylinder head to 65 ft/lbs and then giving it an extra half turn to make sure its OK

With EFI you can read the WB oxygen sensor voltage and set the AFR with reasonable accuracy over the entire rev range ............ and it it wasn't for the non too small point of the bores filling with oil and no oil pressure the engine would still run completely inverted..........

Ian

[300bhp/ton]

Last Sodbury I bought three EFi setups complete apart from the ECU and AFM - inlet manifold, injectors, loom, the lot. I paid between £5 and £20 for each. You need a HP fuel pump (woo). The heads are the same save for a tiny notch where the injector sprays, you can live without it or you can add it with a dremel and a vacuum cleaner while you swap the inlet manifolds...

The sum total of wiring to join it to the rest of the car is about 5 wires - ignition live, fuel pump, coil, and ground.

My tuning laptop (a toughbook no less) cost me £25 off eBay, the tuning software is free to download (and open source) and there's an "auto tune" feature that tweaks the fuel map to a target mixture as you drive. In fact if you fit a wideband O2 sensor you just give the ECU an AFR target map and it constantly tunes itself to hit it to a very high accuracy.

I don't think you can use modern diesels as an argument in a discussion about petrols, my van does the same thing as it's totally fly-by-wire and the ECU is programmed to act as a buffer between the nasty harsh demands of the driver stamping on pedals and the nice smooth gentle responses that are best for the engine and any passing dolphins or pandas. Quite frankly you may as well glue the accelerator to the floor and drive with the other two pedals there's so much lag on the bloody thing

Which is why all the new cars sold these days run carbs - why the F1 boys are tripping over themselves to fit carbs I hear

So an aftermarket race carb versus an out-of-the-box factory ECU? Good test...

Edited to add: Am it picture tiem?

OK lets play:

You're right, it never looks as steep in photos does it?

I think sadly you are taking my comments WAY out of perspective. I never said carb is better than EFI or that new cars should be sold with carbs.

All I've said is that a good carb setup can work very well in many conditions, off roading may not be where it's best suited, but MANY do use it and use it successfullly - I don't think you or anyone else can deny that.

And BTW that isn't a race carb it's an aftermarket add on for the LS1 designed for street use.

So to sum up:

-You like EFI

-I like EFI

-I like and accept that carbs can work (proof is people use them) and that they can make equal power (proof provided by a article)

-You seem not to like carbs and for no aparant reason other than they are old

[300bhp/ton]

Who said anything about trails ? ................. try sitting on a 60 degree plus slope at an angle of 35-40 degrees whilst your winch monkey rigs .......... then see if your carb will allow the engine to tick over ......never mind giving the correct AFR if you punch the gas pedal..............

Ok in this situation its different, but as I don't own a winch I've never experienced such a situation. However, it is just that - a situation. And may not be one many come across while off roading.

As for adjusting your SU's on the driveway with the minimum amount of tools ................ thats a bit like setting the torque on a cylinder head to 65 ft/lbs and then giving it an extra half turn to make sure its OK

I'm not saying it's the best way or even the easiest way to tune, but many do. Pop over to the Mini Forum and talk about tuning SU carbs, it's a common thing they do, swapping needles and playing with the mixture.

With EFI you can read the WB oxygen sensor voltage and set the AFR with reasonable accuracy over the entire rev range ............ and it it wasn't for the non too small point of the bores filling with oil and no oil pressure the engine would still run completely inverted..........

Ian

Have I denied any of this?????

I LIKE EFI, but I also like carbs and have a setup which exceeds expectations, so why should I feel as though I have to change it just to please a couple of bods on the internet, simply because they don't like carbs??

BTW - this has EFI and no I wouldn't change it to carb and yes it is mine:

[Corrode Finger]

Highly Interesting!

But just to get back to the original Question, 3.5 or 3.9?

I assumme that the 3.9 is better cos its bigger?

But

The 3.5 is better cos its not overbored?

So to get my head around what was asked, you kinda pays yer money and makes yer choice?

If you can get or have a 3.9, then go for it/ keep it, abuse it, use it?

My head hurts!!

[300bhp/ton]

Highly Interesting!

But just to get back to the original Question, 3.5 or 3.9?

I assumme that the 3.9 is better cos its bigger?

But

The 3.5 is better cos its not overbored?

So to get my head around what was asked, you kinda pays yer money and makes yer choice?

If you can get or have a 3.9, then go for it/ keep it, abuse it, use it?

My head hurts!!

Yep all are good engines. So go for what ever

[sheeppimp]

all scared of H₂O tho - go diesel

tin hat, flak jacket running for the bunker

[Hybrid_From_Hell]

The 3.9 is fine and as a second hand unit is likley to be a safer bet than the equivalent 4.6.

This is more down to the ECU programs, as the 4.6s have a habit at certain RPMs to run too lean causing internal weak running = heat build up, this is often the case for liner dmage. Mark Adams ECU Guru reprograms these and this is a key part of the equation for performance and longevity.

3.9s ECU have a differeing Map and as such do not have this issue, the 4.6s have been mapped as Mark says "By Committe" ie one wants economy over everything else, another performance, another mid range and yet another emmissions etc, as such the map is a group effort / bodge, and hence the prob with lean at often motorwat cruising RPMs.

With the tolerances of manufactuers, not all 4.6s suffer, and not all are driven in the problem areas, hence why only some get the problem, 3.9s nope, not the same

3.9s CAN have probs, but in the main at lot less than 4.6s, also many V8s do not have servicing done regularly / propoerly to save spending £££s and as such NO V8s like to be left unserviced, its a real issue with a V8 Rover, oil changes and filter and servicing is a MUST for long life.

3.5s tend to have even fewer problems, as virtaully none of the above applies, there were a few Hot wire 3.5s but very few, most were flapper systems, which just do seem to have DNA from Satan in the systems from time to time

In summary

3.9 is better than 3.5 for all sorts of reasons.

4.6 is better than 3.9 but be aware that you need to get a good one

Condition and regular previous servicing for ALL is absolutely paramount

HTH

Nige

[Corrode Finger]

I only posted to head it off at the pass to stop a 'scorpion esque' thread again!

Perhaps that was bad, it was getting entertaining!!

Please resume play after this interval.

Refreshments are at the exit!!

Hat, coat,................ gone!

[Bull Bar Cowboy]

Ok in this situation its different, but as I don't own a winch I've never experienced such a situation. However, it is just that - a situation. And may not be one many come across while off roading.

These situations occur regularly in challenge events. Also whilst taking short cuts or recovering deer around some of the farms I shoot on.

My winch build can be seen here ……. http://forums.lr4x4.com/index.php?showtopi...hydraulic+winch

I'm not saying it's the best way or even the easiest way to tune, but many do. Pop over to the Mini Forum and talk about tuning SU carbs, it's a common thing they do, swapping needles and playing with the mixture.

Have I denied any of this?????

Hmmmmm …………. We seem to have some things in common ……….. in the early to mid 70’s I used to race Mini's and had a small cottage industry business in building race A series engines ………..specializing in the 850, 970 & 1071 engines ………. My real claim to fame is having a lightened flywheel come off an 850 whilst spinning at 8500+ rpm ……….. it made a serious mess of the bellhousing, g/box, and bulkhead. In those days to get that level of RPM we used to lighten al the valve gear as much as possible….. egg shell thin cam followers, drilled pushrods, and almost hand crafted steel rockers. Idle with a lightened flywheel and 649 cam was 2000+ rpm. Biggest problem with the SU is the shear number of available needles ......... its one of the few carbs that could be made to provide non linear fueling ............ not too bad to set up with a stethoscope and some experience..........

I LIKE EFI, but I also like carbs and have a setup which exceeds expectations, so why should I feel as though I have to change it just to please a couple of bods on the internet, simply because they don't like carbs??

BTW - this has EFI and no I wouldn't change it to carb and yes it is mine:

Which ever way you look at it Carbs and also dizzy’s are still very much a compromise solution and have been developed to their mechanical limits………….. I guess this is also true of the RV8 engine ……….. it wasn’t exactly ahead of its time (other than being ali) when it first hit the streets in 1961 in the Buick Special ………..and its not a lot different today….

I'm not suggesting for one minute that you change to EFI ............ I'm just pointing out that carbs have serious deficiencies when used in many off road situations........... however, if it floats your boat then fine..........

Ian

[300bhp/ton]

These situations occur regularly in challenge events. Also whilst taking short cuts or recovering deer around some of the farms I shoot on.

My winch build can be seen here ……. http://forums.lr4x4.com/index.php?showtopi...hydraulic+winch

Hmmmmm …………. We seem to have some things in common ……….. in the early to mid 70’s I used to race Mini's and had a small cottage industry business in building race A series engines ………..specializing in the 850, 970 & 1071 engines ………. My real claim to fame is having a lightened flywheel come off an 850 whilst spinning at 8500+ rpm ……….. it made a serious mess of the bellhousing, g/box, and bulkhead. In those days to get that level of RPM we used to lighten al the valve gear as much as possible….. egg shell thin cam followers, drilled pushrods, and almost hand crafted steel rockers. Idle with a lightened flywheel and 649 cam was 2000+ rpm. Biggest problem with the SU is the shear number of available needles ......... its one of the few carbs that could be made to provide non linear fueling ............ not too bad to set up with a stethoscope and some experience..........

Which ever way you look at it Carbs and also dizzy’s are still very much a compromise solution and have been developed to their mechanical limits………….. I guess this is also true of the RV8 engine ……….. it wasn’t exactly ahead of its time (other than being ali) when it first hit the streets in 1961 in the Buick Special ………..and its not a lot different today….

I'm not suggesting for one minute that you change to EFI ............ I'm just pointing out that carbs have serious deficiencies when used in many off road situations........... however, if it floats your boat then fine..........

Ian

Cool.

You still into the Mini scene?

And ok I conceed that EFI would be better for Challenge events, although I'd personally opt for diesel.

Guess I just need shcooling in some other off road events, lol

[q-rover]

Carb. vs. EFI

Spitfire vs. Messerschmidt Me109.

The Me109 could loose a tailing Spitfire in a dog fight by going vertical

as the Spitfire could't follow for very long.

This has been a useless information announcement.

[300bhp/ton]

Carb. vs. EFI

Spitfire vs. Messerschmidt Me109.

The Me109 could loose a tailing Spitfire in a dog fight by going vertical

as the Spitfire could't follow for very long.

This has been a useless information announcement.

That's not exactly true, there was a half way fix on about the MKIV I think which was coil with a hole in or something, a lady at works came up with the idea, but latter engines where re-engineered I beleive which solved pretty much all of these issues.

BTW - the ME109 wasn't EFI, it was MFI (no no not the shop, but mechanical fuel injection, lol)