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From: Alan Dobbs[SMTP:gulfcmt@flash.net]
Sent: Friday, December 01, 2000 9:23 PM
Subject: RE: [D90] Re: snorkel - impact on power
I do not have the technical data to back up but the 3-inch Centri
pre-breather mounted on our D-90 is to small because I loose a tremendous
amount of HP at high RPMS.
The hose is 2.5 inches from the air filter to the bonnet / driver's fender
then id is 3 inch up to the pre-breather.
I plan on mounting a 4-inch Centri pre-breather and keep 3 inch hose to the
air filter.
Her is our old snorkel version
http://www.yellowdefender.com/accessories/exterior/snorkel/index.htm
And here is the mounted 3 inch Centri
http://www.yellowdefender.com/accessories/exterior/Snorkel2/index.htm
Alan Dobbs
Date: Thu, 17 Sep 1998 00:02:50 -0700
From: "Kelvin Crezee" hd4hls@inficad.com
Subject: [D90] Snorkle
This is a reprint from Ben Mitchell that I had in my archives,
1 2" ABS cap
1 4"->2" ABS Reducer fitting with the lip Dremeled out of the 2" end
1 30-something" length of 2" ABS pipe
1 20-something" length of 2" ABS pipe
2 2" Flex-Ell rubber pipe fittings
1 2" ABS Ell Fittings
2 2" ABS Street Ell Fitting
1 Craftsman ShopVac replacement vacuum hose
1 Black rubber bicycle tube
2 Large ABS tubing supports
2 Large pipe clamps
Take the 30ish" piece of ABS and drill out several large holes in the top. Then slide the 4"->2" reducer fitting over the top of this tube in the wrong direction so it acts as a sort of cover for the holes (which should be positioned so they're completely under the cover. Then put the cap on to cover the open end of the tube.
Take the ABS tubing supports (these are designed to be nailed to something and provide space for zip ties to hold the tube into a toothed notch in the support) and cut off the sides where the attachment points are, leaving you with the notch. Then cut a strip of the bicycle tire and wrap it around your driver side rollbar vertical member and then around the tube. Looking from above, it'll be sort of an "S" shaped wrap. This both protects the rollbar and provides some friction to keep things from sliding around. Get it on there tight; so it holds itself in place by wrapping back on itself and holds the tube up against the rollbar. Then pull the tube away from the rollbar and stick the support in between the tube and the bar. The support will have rubber as it's contact point on either side. Now take the pipe clamp and clamp the tube in position. You should do this twice on the tube - once near the top and once near the bottom.
Now take a Flex-Ell and attach it to the bottom of the tube that's tied into the rollbar, and insert the end of the shorter length of ABS into the other side. Determine the appropriate length for this tubing so that when a standard ell is attached it will center in the middle of the black plastic dummy-vent on the driver's side wing - then cut the tube. Mark the circle that will need to be cut from the vent and remove it from the vehicle. Now center the street ell in that mark and remark the hole to that smaller size. The standard ell will fit over the street ell which will stick up from underneath.
Grind out the material using a dremel tool or something similar, and insert the street ell from underneath, mating it to the standard ell from above.Insert the end of the craftsman vacuum hose into the other end of the street ell and adhere in place with ABS adhesive followed by silicone caulking to seal.
Remove your air cleaner trumpet and cut off the end. Clamp the end of the other flex ell to the trumpet stub, and insert a second street ell into the other end so you have a "U" shaped fitting off the end of the cleaner. Cut the vacuum hose to length and seal it into position in the end of this "U". Now put it all together and seal everything up tight.
You'll also need to remove your air cleaner housing, remove the dumpout valve, and epoxy a threaded fitting on in its place so you can fit a screw cap to seal that up. The stock dumpout valve will not do a good job of preventing water ingress.
None of this requires seriously expensive damage to the vehicle. The only parts you're modifying are the air cleaner housing and the plastic grille cover. Haven't priced these items, but I doubt they're more than $150 together.
- - -Ben
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From: dirk[SMTP:dirk@rust.net]
Sent: Friday, March 31, 2000 5:55 PM
Subject: RE: Raised Air Intake
> ....Anyone have any tips on making a "Home Made" snorkel? Any tips
>would be greatly appreciated....
If you'd like another alternative for some parts:
I'm on my third generation of home made snorkel now and the best set up
performance wise I've had and the best looking (better in my book then the
mantec) is with a:
Centri Precleaner 800-356-4882 on the top. I went with the ex25-3 this is
rated under the rover's max air needs but is right on the money up to about
4500 rpm (they give a max rating after margin of 240cfm). I don't run with
the snorkel all the time, instead I bought a used air cleaner trumpet and
swap if I'm going off roading. Up until then, the snorkel just feeds cool
air into the engine bay.
A section of 3 inch exhaust tube bent to order by a muffler shop; and
a section of 3 inch RFH durable rubber flexhose from Airhandling systems
800-376-3828.
If you run the formula's, any snorkel will restrict the engine short of a
five inch dia tube... sorry that just won't cut it. While our computers
can make some adjustment?????, if you drive at altitude I'd check for
fouled plugs after running with the snorkel for awhile.
Good luck,
Dirk Tischer
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From: Noel Dancy[SMTP:noeldancy@hotmail.com]
Sent: Tuesday, April 25, 2000 8:26 AM
Subject: [D90] Raised Air Intake. Was Headlight Relay Placement
Chris. I have removed the large plastic moulding under the Passenger (R/H)
wing. This feeds air into the heater air intake. I cut the end off the
trumpet on the engine air filter, and fitted a 2.5" inch flexy pipe. Routed
this under/alongside the windscreen washer bottle upto the grille on the R/H
wing. Cutting a hole at the rear of the grille. I had a snorkel already (W&H
Wheelcarriers), that I have used. The heater air intake is about 4"
diameter, I sleeved this down to 2.5" by using a plastic pudding basin. I
then took another length of 2.5" flexy to the front area of the wing grille
and cut another hole. I am getting a metal plate made to replace the plastic
grille that will have the two pipes with a "scoop/cowl" on the heater
intake. A simple bung in the cowl when wading stops the heater flooding.
Result. Minimum hose length to the engine air intake, Snorkel out of the
drivers line of sight on the right door post, and increased heater input
with increased road speed. If you really need a bigger air intake get a
washer bottle from the new Defender TD5, this mounts on the L/H wing and
would open up the R/H grille completely. Though the 2.5" trunking seems
ample, ie seat of the pants test and she pulls like a train in all gears.
If you need greater heater output try putting a small fan on the heater air
intake. We used to increase VW Campervan heater efficiency by fitting a mini
heater fan into the ducting, worked a treat!
PS: If your heater output is not good, check the fit between the heater
intake and the plastic moulding under the R/H wing. There's a silly plastic
sleeve and a bit of foam joining the two together. On mine it was a "slack"
fit.
Noel D. (now with less sand in the air filter)
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From: Clarke Williams[SMTP:clarkewilliams@halcyon.com]
Sent: Monday, April 03, 2000 11:09 AM
Subject: [D90] Centri (was Home-made snorkel)
>What's all this about Cetntri pre-cleaners needing to be mounted vertically?
>Right on their home page ( http://www.centriprecleaner.com ) in
>big bold letters it says:
>
>" Mounts at any angle, including inverted! "
YOU ARE ABSOLUTELY CORRECT!
After posting that message yesterday I got to thinking about it. I didn't
check the web site -- I took a Centri that is not currently mounted and did
a "vacuum cleaner test" by connecting the outlet of the Centri Pre-Cleaner
to a shop vac and dumping sand into the inlet. I put the Centri at various
angles and it popped the sand out the outlet vent just fine. The Centri is
really pretty neat to watch in operation. With a clean white cloth as a
filter, you can see how much crud the Centri pulls out of the airflow.
My only excuse is old age and fading brain cells, I guess. Maybe I was
thinking of the SyKlone?
(extraneous verbage clipped - ed.)
Clarke Williams
------------------------
Date: Wed, 23 Sep 1998 10:42:22 -0700
From: Larry Michelon kismet2@erols.com
Subject: [D90] Performance Gains
I did a search to find the losses of cutting of the "horn" on the air filter housing (D90's and Classic RR's). At the same time I stumble across the other notes that Jim Allen had writting to the list. Whether or not you believe Jim as a very knowledgable person, he has documentation (often first hand) of his findings. Sorry if it's so long.
Below are direct quotes from Jim's postings. Find out more about Jim at 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
======================================================
AIR FILTER HOUSING "HORN":
Good on you for not hacking off the trumpet! Would you believe that
doing so aftually costs hp. Did some dyno tests a while back and found
that altering (i.e. hacking off) or removing the horn cost between 2&3
hp. Probably couldn't feel it but the drop is there. The effect gets worse
as the rpms rise but there appears to be a definite disruption of airflow
at about 3000rpm because there is a ripple in the torque curve that goes
away with the horn installed.
As an aside, a larger displacement engine might need a larger
(but similarly designed) horn but when we flow bench tested the air
cleaner assembly, it had more airflow capacity than a 4.2-4.5L engine
needs to achieve 5500rpm. It gests dicey airflowwise for a bigger engine
but as long as you don't need 5500 rpm often, I wouldn't sweat it.
Jim Allen