The tinkering has started
Discussion
As said, I have started tinkering under the bonnet, it is a 400 flapper. List of new parts so far:
New plugs
New leads
New dizzy cap
New rotor arm
Ordering a new air filter, Question---Pipercross or K&N
Fuel pressure is running at 40,(got an in line gauge fitted.) goes up slightly when revved- 44-46, but at static revs,2k 3k, it settles back to 40. Is this too high????
The car has no air filter fitted, it has a flexible hose going down to the front of the engine with a metal grill over the end and what remains of an old pair of thick women's tights over that as a filter. What effect will this have on fuelling???
My idea is it will cause rich running, true or not????
Plugs were fairly black so rich running somehow. Any other suggetions/comments welcome
New plugs
New leads
New dizzy cap
New rotor arm
Ordering a new air filter, Question---Pipercross or K&N
Fuel pressure is running at 40,(got an in line gauge fitted.) goes up slightly when revved- 44-46, but at static revs,2k 3k, it settles back to 40. Is this too high????
The car has no air filter fitted, it has a flexible hose going down to the front of the engine with a metal grill over the end and what remains of an old pair of thick women's tights over that as a filter. What effect will this have on fuelling???
My idea is it will cause rich running, true or not????
Plugs were fairly black so rich running somehow. Any other suggetions/comments welcome
Well, you don't know for certain that the guage is accurate, it could be +/- 5psi! Even if it is, 4psi or so over isn't much but could account for the sooty plugs. Maybe it was tuned for top-end and actually spent most of its time round town.
Tights eh
In my day (well OK, GrahamW's) they were mostly used as fan belts 
However they may be freer-flowing than a K&N, but how would you tell?
Tights eh
In my day (well OK, GrahamW's) they were mostly used as fan belts However they may be freer-flowing than a K&N, but how would you tell?
TOPTON said:
Fuel pressure is running at 40,(got an in line gauge fitted.) goes up slightly when revved- 44-46, but at static revs,2k 3k, it settles back to 40. Is this too high????
The car has no air filter fitted, it has a flexible hose going down to the front of the engine with a metal grill over the end and what remains of an old pair of thick women's tights over that as a filter. What effect will this have on fuelling???
Plugs were fairly black so rich running somehow. Any other suggetions/comments welcome
One speculates a pair of tights will offer less air resistance than a proper filter but as the flapper measures the air molecules (volume at a particular temperature) entering the system, theoretically the type of filter would make little or no difference to mixture control. The car has no air filter fitted, it has a flexible hose going down to the front of the engine with a metal grill over the end and what remains of an old pair of thick women's tights over that as a filter. What effect will this have on fuelling???
Plugs were fairly black so rich running somehow. Any other suggetions/comments welcome
A "better" filter may allow a higher air flow and therefor more air available, but wont affect mixture control as managed by the AFM, ECU and other sensors. However a completely blocked filter may fook thing up somewhat.
A 3.5 Flapper system fuel pressure is usually set for 36 psi maximum and vary between 26 psi and 36 psi when running (depending upon engine load). Your 4.0 may require 12% higher fuel pressure depending upon AFM settings, a maximum of 40 psi varying between 30 and 40 psi.
Your 44-46 psi (top number) seems obscene if the rest of the system is "standard" and will give at least 11% (maybe much more) overfuelling across the whole range, very sooty plugs and crap economy.
Whatever? "Sooty Plugs" usually equals "Overfuelling", so it's a simple process to gradually reduce the fuel pressure until the cruising plug condition becomes a normal light straw colour and then re-measure the pressure to see what you have gotton down to.
Alternatively cut to the chase and set the fuel pressure to the workshop manual recommendation (36 or 40 - someone might know?) to see if the plug condition normalises and the moolah stays longer in the wallet.
If you need to study any typical component function CLICK HERE
"A 3.5 Flapper system fuel pressure is usually set for 36 psi maximum and vary between 26 psi and 36 psi when running (depending upon engine load). Your 4.0 may require 12% higher fuel pressure depending upon AFM settings, a maximum of 40 psi varying between 30 and 40 psi.
Your 44-46 psi (top number) seems obscene if the rest of the system is "standard" and will give at least 11% (maybe much more) overfuelling across the whole range, very sooty plugs and crap economy.
Whatever? "Sooty Plugs" usually equals "Overfuelling", so it's a simple process to gradually reduce the fuel pressure until the cruising plug condition becomes a normal light straw colour and then re-measure the pressure to see what you have gotton down to."
I'd have to disagree with honestJohn here. In my experience, and the experience of a few others, the flapper system when fitted to the 3.9/4.0 needs around 50psi base rail pressure to give good fuelling (If you're on standard injectors).
Your sooty plugs only indicate what your engine is doing at idle unless you did a plug chop. At 40psi my car runs dangerously lean, i would advise you to leave the pressure as is, and either spend 50 quid on a rolling road run to see exactly what your fuelling is doing or £150 on a wideband lambda. Blindly lowering the fuel pressure could cause damage, it's bloody hard to hear any pinking over the sound of a mighty wedge!
Your 44-46 psi (top number) seems obscene if the rest of the system is "standard" and will give at least 11% (maybe much more) overfuelling across the whole range, very sooty plugs and crap economy.
Whatever? "Sooty Plugs" usually equals "Overfuelling", so it's a simple process to gradually reduce the fuel pressure until the cruising plug condition becomes a normal light straw colour and then re-measure the pressure to see what you have gotton down to."
I'd have to disagree with honestJohn here. In my experience, and the experience of a few others, the flapper system when fitted to the 3.9/4.0 needs around 50psi base rail pressure to give good fuelling (If you're on standard injectors).
Your sooty plugs only indicate what your engine is doing at idle unless you did a plug chop. At 40psi my car runs dangerously lean, i would advise you to leave the pressure as is, and either spend 50 quid on a rolling road run to see exactly what your fuelling is doing or £150 on a wideband lambda. Blindly lowering the fuel pressure could cause damage, it's bloody hard to hear any pinking over the sound of a mighty wedge!
Edited by B-Reight on Wednesday 21st April 22:34
Edited by B-Reight on Wednesday 21st April 22:35
grahamw48 said:
I would recommend having a rolling road session.
Had my (hotwire) 400 set up last year, and finished up having an adjustable fuel valve fitted too, to correct weak mixture at high revs.
Well worth it for peace of mind, plus the bonus of an extra 9 bhp and improved fuel economy.
Your last one made pretty decent power didn't it, nearly 240bhp iiRC. Hows the new one going, looks a beaut (even if it does have a surf board screwed to the boot Had my (hotwire) 400 set up last year, and finished up having an adjustable fuel valve fitted too, to correct weak mixture at high revs.
Well worth it for peace of mind, plus the bonus of an extra 9 bhp and improved fuel economy.
)Hi Ben.
The new one is a really nice car thanks. Until I've had a new exhaust put on (end of the week), it's probably unfair to compare the two performance-wise, but she's already pretty quick and healthy-sounding.
Doesn't feel as torquey as the 400, but again, we'll see what the exhaust does. The present one is blowing all over the place.
There is a definite power surge at 3,500 revs, whereas the 400 was much the same right the way up...different cam' I expect.
Funnily enough the spoiler doesn't look bad at all (IMO)with the colour of the car and the flared arches,etc.
My only concern is the extra weight slowing me down.
I compensate by tossing everything out of the boot and relying on the AA.
I'll probably take this car up to the R/R too, but as ever...prepare to be disappointed with the bhp. It's how they drive on the road that counts.
This car for instance has a much slicker gear change than the 400, so makes it less of a chore to 'make progress'.
The new one is a really nice car thanks. Until I've had a new exhaust put on (end of the week), it's probably unfair to compare the two performance-wise, but she's already pretty quick and healthy-sounding.
Doesn't feel as torquey as the 400, but again, we'll see what the exhaust does. The present one is blowing all over the place.
There is a definite power surge at 3,500 revs, whereas the 400 was much the same right the way up...different cam' I expect.
Funnily enough the spoiler doesn't look bad at all (IMO)with the colour of the car and the flared arches,etc.
My only concern is the extra weight slowing me down.
I compensate by tossing everything out of the boot and relying on the AA.
I'll probably take this car up to the R/R too, but as ever...prepare to be disappointed with the bhp. It's how they drive on the road that counts.
This car for instance has a much slicker gear change than the 400, so makes it less of a chore to 'make progress'.
Edited by grahamw48 on Wednesday 21st April 23:37
, just a boot full of tools! Poledriver said:
Out of interest, my wedge has the J.E. engineering 4.5 litre engine with larger valves and flowed/ported head. Jaguar flapper and injectors. What would you recommend I set the fuel pressure to?
Get it on the rolling road and check the fuelling, there really is no magic figure regarding fuel pressures when your running a non standard setup like that.
The car has a standard fuel pressure regulator, as far as I can tell, it certainly isn't adjustable but it may be a bigger flow to standard looking one. Maybe time for a new one.
I was under the impression (as far as the tights go) that no or little air filtering would equate to more air/more fuel, hence rich running. Rather like if the filter was blocked it would run rich. It backfires sometimes, even under gentle acceleration, the crackle and pops I can live with.
Cant really fiddle with anything else until air filter arrives. Then I can set/check the timing with all new stuff fitted.
Living out in the sticks doesn't give much opportunities for rolling road sessions, I cant even think of one around here. But I am willing to travel a bit if anyone knows someone in the north (far north, west cumbria. Not quite Scotland but close)
ETA someone mention fuel economy, Whats that???? think mine is about 15 to the gallon at the mo
I was under the impression (as far as the tights go) that no or little air filtering would equate to more air/more fuel, hence rich running. Rather like if the filter was blocked it would run rich. It backfires sometimes, even under gentle acceleration, the crackle and pops I can live with.
Cant really fiddle with anything else until air filter arrives. Then I can set/check the timing with all new stuff fitted.
Living out in the sticks doesn't give much opportunities for rolling road sessions, I cant even think of one around here. But I am willing to travel a bit if anyone knows someone in the north (far north, west cumbria. Not quite Scotland but close)
ETA someone mention fuel economy, Whats that???? think mine is about 15 to the gallon at the mo
Edited by TOPTON on Thursday 22 April 08:30
B-Reight said:
I'd have to disagree with honestjohn here. In my experience, and the experience of a few others, the flapper system when fitted to the 3.9/4.0 needs around 50psi base rail pressure to give good fuelling (If you're on standard injectors).
OK Ben, thanks for the correction. I knew the fuel pressure would be higher than 36, but clearly my arithmetic is corrupted. A 10 - 12% increase in cylinder volume clearly does not equal a 10 to 12% increase in breathed air and therefor, metered fuel. Much more of both is needed so, do you think the AFM is also adjusted accordingly? Must be!Also I just realised its probably not running an adjustable FPR. I'll go back and make edits to my observations. If these machines rely on 50 psi base pressure this car is still 4 psi shy of that number so it may even be underfuelling as regards fuel pressure.
I'd have to say that does seem wrong because it was not clear to me that the sooty plugs were caused at idle only, Normally one assumes that such a report results from a driving situation so I still stand by
honestjohntoo said:
Whatever? "Sooty Plugs" usually equals "Overfuelling"
Mind you given the host of other things that cause overfuelling, it could be an expensive journey of discovery if replacing components until a fault is uncovered, or perhaps the rolling road is the only solution to setting up and uncovering the faults, as opposed to component analysis? All of that is outside my experience so lots still to learn.[quote=B-Reight]
I'd have to disagree with honestJohn here. In my experience, and the experience of a few others, the flapper system when fitted to the 3.9/4.0 needs around 50psi base rail pressure to give good fuelling (If you're on standard injectors).
[quote]
Agreed, My 400SE was also dangerously lean at high RPM with a baseline fuel pressure of 40psi. I also had to goto 50psi to get the high load fueling correct (the lean mixture possibly explains the engine failure the car had too) It's now too rich at 1500rpm but that's another story, it goes at lot better than it used to !
Either get it on the rollers or if you plan to do some tweaking get yourself a wideband as it will soon pay for itself.
For reference my 400SE has a standard chimp 3.9 lump, RT manifolds and exhaust system, a set of ACT carbon trumpets and K&N that looks about the right size for a lawnmover....
I'd have to disagree with honestJohn here. In my experience, and the experience of a few others, the flapper system when fitted to the 3.9/4.0 needs around 50psi base rail pressure to give good fuelling (If you're on standard injectors).
[quote]
Agreed, My 400SE was also dangerously lean at high RPM with a baseline fuel pressure of 40psi. I also had to goto 50psi to get the high load fueling correct (the lean mixture possibly explains the engine failure the car had too) It's now too rich at 1500rpm but that's another story, it goes at lot better than it used to !
Either get it on the rollers or if you plan to do some tweaking get yourself a wideband as it will soon pay for itself.
For reference my 400SE has a standard chimp 3.9 lump, RT manifolds and exhaust system, a set of ACT carbon trumpets and K&N that looks about the right size for a lawnmover....
B-Reight said:
My 390 has exactly the same power surge at 3.5k and revs past 6k which makes it fun to keep on the boil, and once into third gear very quickly into illegal speeds 
My 390 revs past 6000 although I try to avoid so doing, it doesn't sound particularly nice up there! I wouldn't say there was a power 'surge' at 3500, maybe a bit more of a bulge on the graph but otherwise just a constant push.Just got back from a 150-mile round trip to check out a bike, had the satnav on and the speedo is within 1MPH to well over 90! Er, kph, ossifer...
Which begs the question, just how fast WAS it going when I ran it off the clock at 160 a few years back?! On that private test track, obviously Might have to go back and do it again... 
Gassing Station | Wedges | Top of Page | What's New | My Stuff