Sergei
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This is extraction from d-90.com of things that arent existant anymore in original source. All below belongs to Jim Allen.
Jim Allen
http://www.fourwheeler.com/techline/lrover/index.html.
ON K&N FILTERS:
Item 1) I have several test (the sources of which I posted yesterday) that puts the K&N at least equal to a paper filter. I'm doing more research on this but so far K&Ns are rated as 96.8-97.8% efficient (K&N claims 97%). The info I have on paper filters rates them from 92-96% efficient (the 92% info is about ten years old)
Item 2) I don't understand how you can deduce that a lower restriction filter equals less power at low rpms? I can't account for a Honda but I have dyno charts (from a Disco, RR 4.0SE and RR Classic) that's how that there is little benifit to K&Ns at low rpm (but no loss) and a 4.5-55hp increase at 5000rpm. I was there during the tests that were being done for a series of articles I was working on. There are other tests in magazines that also show similar results.
The whole game with performance air filters is airflow, so until the engine really starts to wheeze at the upper end, it can work OK with any filter that gives it enough air for a particular speed. Based on the tests I ran, the OE filter starts to wheeze at about 3500rpm because that's when the extra power starts to come in. We ran tests on the air filter housings themselves and found that, with the exception of the RR 4.0SE, they were no restriction to power up to the 5500 rpm redline.
Since few of us see 5000rpm, the 4.5-5.5hp may not be a big deal, though my seat of the pants says the engine is snappier on acceleration. After the dyno tests, I drove the 4.0SE and the Disco from the dyno in California back to Colorado and noted an increase in mileage over the trip out in stock condition, but since there were other mods to the vehicles at that point, I can't attribute it to the filter. A non-Rover magazine project vehicle I am currently working on has noted an increase in mileage that I can definately attribute to the filter, but the vehicle had a particularly inefficient unit as stock.
Item 2A) Upon reflection, a carbureted engine might have a problem going to a free flow filter because it was originally jetted for a restictive filter. If you were to re-jet the carb, power would be restored or increased. I guess I'd need to know the details of the test your mentioned.
The bottom line is that for most folks, the power changes and mileage increase would be minimal - but there! The main benifits would be a higher capacity to carry dirt, the ability to handle water and the option to clean the filter forever instead of replacing it sooner or later.
The debate rages on!
Jim Allen
======================================================
ON EXHAUST MODIFICATIONS:
Some exhaust information.
1) Lets get the terminology right - or at least consistant for discussion. The exhaust "manifolds" are the cast iron pieces that bolt to the engine. The "downpipes" or "header pipes" are the exhaust pipes that connect the manifolds to the "Y", where the two downpipes connect into a single pipe.
2) If your Rover has a pair small looking pipes (about 1-1/2" - one from each bank) with or without cats, you have a mondo restrictive setup such as the '87-88 NAS system came with. The '87-88 NAS systems generate 5-8psi backpressure with their triple cats and small headpipes.
3) If your Rover has two pipes on each side, you have the beginnings of a good system. This appeared on non-cat EFI V8s starting about '86. 4) The factory EFI manifolds are adequate for off-road service and operation in power levels up to about 25% more than stock (figure about 200hp).
5) The '89-later exhaust systems are decent, generating about 2-4psi backpressure. Thy use 2" headpipes and 2-1/2" pipes. Muffler changes will produce some slight increases in power.
6) The Rover EFI system limits the amount of power you can get with modifications. Dyno tests I personally performed barely yielded a 5% imnprovement with a very well designed performance exhaust. This was not the fault of the exhaust, but due to the limitations in the fuel injection system.
7) The small headpipes (one on each side) are the main impediment to power on the rigs so equipped.
8) You can install an '89-later exhaust system (including cats) onto a '87-88 for an improvement in power but you will need to change the square trans. crossmember with a later round one, plus relocate some hangers. A 3.9L control unit (the whole thing) will further enhance performance but the 3.5L NAS "low-lift" cam will also slow you down. Consider a 3.9L or mild aftermarket cam.
9) Here's a very cost effective blueprint that I know works (10-12 built with good results). If you alter it much, I make no claims to how it will work.
1) If emissions regulations aren't an issue, get the aforementioned dual-on-each-side downpipes and open their collectors up to match a 2" pipe. Otherwise, use an entire '89 or later assy complete with cats.
2) Get hold of the "Y" pipe assy from an '89-later 3.9L RR. Used is ok. It's got 2" pipes. Open the collectors (where the dual downpipes on each side meet) to fit the 2" pipe and section in the 3.9L Y pipes. Alternately, you can have something like this made but the OE LR "Double D" collector flows well.
2) From the second "Y" use 2-1/2" pipe in a short section to a front muffler. Use a free flow design.
3) From out of the first muffler, use 2-1/4" pipe. Make the pipe follow the original path and if you want a quiet system, add a second, smaller free flow muffler or resonator.
4) Add an exhaust tip of your choosing.
5) Not sure how this system would do with the "big block" 4.5 & bigger engines. Should be OK for normal use, off-road, etc. If high revs and power were desired, probably not a good choice but then a Tri-Y system isn't a good choice where power & rpm capability is desired over torque and economy anyhow.
Why "Tri-Y" this works is that inside your manifolds, the exhaust runners are paired giving two outlets. On the left bank, cyl 1 & 5 are paired and 3 & 7. The dual downpipes connect them about 2 feet down from the manifold. The last Y connects the two banks into a single pipe. A total of 3 "Ys" from head to main pipe. Ever hear of the "Tri-Y" concept?
A "Tri-Y" scavanges better at low speeds than a standard exhaust system. Lets work on the left bank again. Cyl. #1 fires and exhausts and the hot gasses flow out the manifold and down the pipes. As it passes the runner from #5 cyl, the flow creates a partial negative pressure in that runner. When #5 ex. valve opens, the exhast is effectively "sucked" out and the cylinder is cleared of exhaust just that much better. The same thing happens at the next Y. The pulses alternate and "draw" the flow from the opposite pipe. The same thing happens at the third Y. In this case, the runner-to-Y lengths are not optimised but the effect produces a noticable increase in scavanging and is a cost effective modification. It tends to enhance low end to about 2500rpm and as the rpms increase, the effect gradually lessens and by 4000 rpm, is essentially nullified. At that point, the free flow mufflers and larger pipes are just outgassing large amounts with little finesse. I used to scavange 3.9L Y pipes and cut sections out to do this on customers cars. Had to buy the double downpipes, though. Five years ago, the '86 dual downpipes were still in the parts books.
The reason for the single pipe and the larger pipe at the front of the system is temperature.At the front of the system, the exhaust is hot and expanded. By the time is gets though lolligagging in the first muffler, it has cooled considereably. What happens when you take a water hose of 1/2" diameter and neck it out to 3/4"? What flowed quickly in the 1/2" slows considerably as it goes into the 3/4". A similar thing happens to exhaust flow. If it exits the muffler into a large pipe, the flow slows and tends to back up. A slightly smaller pipe tends to maintain the flow rate.
Jim Allen
==========================================
ON IGNITION TIMING:
No knock sensor on RRs before the '95 4.0L engine with the distributorless ignition system with GEMS EFI. I did dyno tests on high compression (9.35:1) 3.9L engines ('94 era) and found a, believe it or not, 15hp increase in power (at 5000rpm) and 28lb-ft of torque (at 2500rpm) increase by setting the timing at 12BTDC. Similar, but lower, results came from a '91 low-comp 3.9L.
Subsequent "plug-chop" test showed no detonation problems at that timing setting if premium fuel was used and the temperature was not consistantly over 90 degrees. I recommend no more than 9BTDC for temps consitantly over 90-100 degrees (like Phoenix or desert towns..
Low compression (8.13) engines can run up to 14BTDC but sometimes you can cause a slight lobe at idle - but not always.
In any case, you will need to reset your base idle speed.
Jim Allen
==================================================
SNORKELS FOR COOLER AIR:
If you mean the conical filter, then the power went up about 1.5hp over the factory filter with a K&N in it. The reservation I have is that its a completely open element. Open to more dirt, open to water and open to heat. The OE filter draws more or less cool air from the front of the eng. compartment. The open filter is going to suck up lots of hot air from the ex. manifold.
I just finished some dyno tests where we compared power readings with "cool" and "hot' intake air in a diesel engine. The temp rise from 88 degrees to 155 degrees caused a 9hp drop in power. From 55 degrees to 138 degrees caused an 11 hp drop. Cool, dense air is what the engine wants. This is why the restriction of a snorkal can be partially or fully cancelled (depends on lots o stuff) by the cool air. just some thoughts!
Jim Allen
Jim Allen
http://www.fourwheeler.com/techline/lrover/index.html.
ON K&N FILTERS:
Item 1) I have several test (the sources of which I posted yesterday) that puts the K&N at least equal to a paper filter. I'm doing more research on this but so far K&Ns are rated as 96.8-97.8% efficient (K&N claims 97%). The info I have on paper filters rates them from 92-96% efficient (the 92% info is about ten years old)
Item 2) I don't understand how you can deduce that a lower restriction filter equals less power at low rpms? I can't account for a Honda but I have dyno charts (from a Disco, RR 4.0SE and RR Classic) that's how that there is little benifit to K&Ns at low rpm (but no loss) and a 4.5-55hp increase at 5000rpm. I was there during the tests that were being done for a series of articles I was working on. There are other tests in magazines that also show similar results.
The whole game with performance air filters is airflow, so until the engine really starts to wheeze at the upper end, it can work OK with any filter that gives it enough air for a particular speed. Based on the tests I ran, the OE filter starts to wheeze at about 3500rpm because that's when the extra power starts to come in. We ran tests on the air filter housings themselves and found that, with the exception of the RR 4.0SE, they were no restriction to power up to the 5500 rpm redline.
Since few of us see 5000rpm, the 4.5-5.5hp may not be a big deal, though my seat of the pants says the engine is snappier on acceleration. After the dyno tests, I drove the 4.0SE and the Disco from the dyno in California back to Colorado and noted an increase in mileage over the trip out in stock condition, but since there were other mods to the vehicles at that point, I can't attribute it to the filter. A non-Rover magazine project vehicle I am currently working on has noted an increase in mileage that I can definately attribute to the filter, but the vehicle had a particularly inefficient unit as stock.
Item 2A) Upon reflection, a carbureted engine might have a problem going to a free flow filter because it was originally jetted for a restictive filter. If you were to re-jet the carb, power would be restored or increased. I guess I'd need to know the details of the test your mentioned.
The bottom line is that for most folks, the power changes and mileage increase would be minimal - but there! The main benifits would be a higher capacity to carry dirt, the ability to handle water and the option to clean the filter forever instead of replacing it sooner or later.
The debate rages on!
Jim Allen
======================================================
ON EXHAUST MODIFICATIONS:
Some exhaust information.
1) Lets get the terminology right - or at least consistant for discussion. The exhaust "manifolds" are the cast iron pieces that bolt to the engine. The "downpipes" or "header pipes" are the exhaust pipes that connect the manifolds to the "Y", where the two downpipes connect into a single pipe.
2) If your Rover has a pair small looking pipes (about 1-1/2" - one from each bank) with or without cats, you have a mondo restrictive setup such as the '87-88 NAS system came with. The '87-88 NAS systems generate 5-8psi backpressure with their triple cats and small headpipes.
3) If your Rover has two pipes on each side, you have the beginnings of a good system. This appeared on non-cat EFI V8s starting about '86. 4) The factory EFI manifolds are adequate for off-road service and operation in power levels up to about 25% more than stock (figure about 200hp).
5) The '89-later exhaust systems are decent, generating about 2-4psi backpressure. Thy use 2" headpipes and 2-1/2" pipes. Muffler changes will produce some slight increases in power.
6) The Rover EFI system limits the amount of power you can get with modifications. Dyno tests I personally performed barely yielded a 5% imnprovement with a very well designed performance exhaust. This was not the fault of the exhaust, but due to the limitations in the fuel injection system.
7) The small headpipes (one on each side) are the main impediment to power on the rigs so equipped.
8) You can install an '89-later exhaust system (including cats) onto a '87-88 for an improvement in power but you will need to change the square trans. crossmember with a later round one, plus relocate some hangers. A 3.9L control unit (the whole thing) will further enhance performance but the 3.5L NAS "low-lift" cam will also slow you down. Consider a 3.9L or mild aftermarket cam.
9) Here's a very cost effective blueprint that I know works (10-12 built with good results). If you alter it much, I make no claims to how it will work.
1) If emissions regulations aren't an issue, get the aforementioned dual-on-each-side downpipes and open their collectors up to match a 2" pipe. Otherwise, use an entire '89 or later assy complete with cats.
2) Get hold of the "Y" pipe assy from an '89-later 3.9L RR. Used is ok. It's got 2" pipes. Open the collectors (where the dual downpipes on each side meet) to fit the 2" pipe and section in the 3.9L Y pipes. Alternately, you can have something like this made but the OE LR "Double D" collector flows well.
2) From the second "Y" use 2-1/2" pipe in a short section to a front muffler. Use a free flow design.
3) From out of the first muffler, use 2-1/4" pipe. Make the pipe follow the original path and if you want a quiet system, add a second, smaller free flow muffler or resonator.
4) Add an exhaust tip of your choosing.
5) Not sure how this system would do with the "big block" 4.5 & bigger engines. Should be OK for normal use, off-road, etc. If high revs and power were desired, probably not a good choice but then a Tri-Y system isn't a good choice where power & rpm capability is desired over torque and economy anyhow.
Why "Tri-Y" this works is that inside your manifolds, the exhaust runners are paired giving two outlets. On the left bank, cyl 1 & 5 are paired and 3 & 7. The dual downpipes connect them about 2 feet down from the manifold. The last Y connects the two banks into a single pipe. A total of 3 "Ys" from head to main pipe. Ever hear of the "Tri-Y" concept?
A "Tri-Y" scavanges better at low speeds than a standard exhaust system. Lets work on the left bank again. Cyl. #1 fires and exhausts and the hot gasses flow out the manifold and down the pipes. As it passes the runner from #5 cyl, the flow creates a partial negative pressure in that runner. When #5 ex. valve opens, the exhast is effectively "sucked" out and the cylinder is cleared of exhaust just that much better. The same thing happens at the next Y. The pulses alternate and "draw" the flow from the opposite pipe. The same thing happens at the third Y. In this case, the runner-to-Y lengths are not optimised but the effect produces a noticable increase in scavanging and is a cost effective modification. It tends to enhance low end to about 2500rpm and as the rpms increase, the effect gradually lessens and by 4000 rpm, is essentially nullified. At that point, the free flow mufflers and larger pipes are just outgassing large amounts with little finesse. I used to scavange 3.9L Y pipes and cut sections out to do this on customers cars. Had to buy the double downpipes, though. Five years ago, the '86 dual downpipes were still in the parts books.
The reason for the single pipe and the larger pipe at the front of the system is temperature.At the front of the system, the exhaust is hot and expanded. By the time is gets though lolligagging in the first muffler, it has cooled considereably. What happens when you take a water hose of 1/2" diameter and neck it out to 3/4"? What flowed quickly in the 1/2" slows considerably as it goes into the 3/4". A similar thing happens to exhaust flow. If it exits the muffler into a large pipe, the flow slows and tends to back up. A slightly smaller pipe tends to maintain the flow rate.
Jim Allen
==========================================
ON IGNITION TIMING:
No knock sensor on RRs before the '95 4.0L engine with the distributorless ignition system with GEMS EFI. I did dyno tests on high compression (9.35:1) 3.9L engines ('94 era) and found a, believe it or not, 15hp increase in power (at 5000rpm) and 28lb-ft of torque (at 2500rpm) increase by setting the timing at 12BTDC. Similar, but lower, results came from a '91 low-comp 3.9L.
Subsequent "plug-chop" test showed no detonation problems at that timing setting if premium fuel was used and the temperature was not consistantly over 90 degrees. I recommend no more than 9BTDC for temps consitantly over 90-100 degrees (like Phoenix or desert towns..
Low compression (8.13) engines can run up to 14BTDC but sometimes you can cause a slight lobe at idle - but not always.
In any case, you will need to reset your base idle speed.
Jim Allen
==================================================
SNORKELS FOR COOLER AIR:
If you mean the conical filter, then the power went up about 1.5hp over the factory filter with a K&N in it. The reservation I have is that its a completely open element. Open to more dirt, open to water and open to heat. The OE filter draws more or less cool air from the front of the eng. compartment. The open filter is going to suck up lots of hot air from the ex. manifold.
I just finished some dyno tests where we compared power readings with "cool" and "hot' intake air in a diesel engine. The temp rise from 88 degrees to 155 degrees caused a 9hp drop in power. From 55 degrees to 138 degrees caused an 11 hp drop. Cool, dense air is what the engine wants. This is why the restriction of a snorkal can be partially or fully cancelled (depends on lots o stuff) by the cool air. just some thoughts!
Jim Allen
Specially after reading all that stuff.
