I think I might have found the cause of my car's lack of power. To give credit where it is due, it was Stickbuilder's thread about modifying the airbox that pointed me in the right direction. In that, he mentions that the fresh-air snorkel appears to be quite restrictive. I went out to the car and had a look at mine. As I have modified the airbox by removing the hot air duct and the flapper, and plugging the hole where it was, the snorkel is now the only source of air for the engine. The diameter of the end of the snorkel did seem to be quite small, smaller in fact, by a good bit, than how I remembered the diameter of the throttle body I cleaned the previous afternoon. I went and got a ruler, which confirmed my suspicions---the throttle body is 55 mm, the end of the snorkel is only 42. I could see how that might be a problem, so I removed the vertical part of the snorkel, which gave an intake opening of 55 mm diameter. Went for a drive, and the car did seem noticeably more responsive, though still not quite up to what I remember the other one as having been. I'll try to get the rest of the snorkel off before I go anywhere tomorrow, and see if that makes any additional improvement. If it does, I will have to figure out how to fabricate a replacement snorkel of adequate dimensions, as I like the shape of it, which looks like it would be very effective at keeping water, insects and other debris out of the airbox. The only thing I can't figure out is why it is so undersized to begin with----it seems to me that the engine would have to draw its air from both the cold and warm air intakes at all times to breathe adequately.

As a footnote, I will mention that on my 740, which ran so well, that the flap was stuck in the hot air position, and the hose was removed, so it was getting all its air through the one hot-air opening (of which I don't know the exact dimension, but it's not all that big---I'll dig up the 740 airbox and measure it when I get a chance)

I had a power problem with my 91 245 M47. Also knocking-pinging and hard starting. I mentioned it to you.

I drove ~ 350 miles today, mostly highway speed. It's fine - perhaps a teeny bit sluggish compared to my 92 AT. I could almost feel it run stronger & stronger as I drove it on the interstate today.

Here's what I did: new fuel filter; new main & lift pumps; new plugs, cap, rotor, wires; cleaned throttle body; removed airbox flap; flushed the engine w/ kerosene through intake port (which I've been doing to older cars since the 1960s). I also removed the snorkel and then put it back on - I don't think it made a difference.

This car had been sitting for ~4 years. I think I had 3 problems: 1) Old gas; 2) varnish deposits in the engine; 3) bad in-tank pump. The rest of the part-changes above were superfluous.

You bought yours at an auction. Perhaps it sat for a while. Perhaps driving it will help.

What kind of transmission is in the car? Is it an auto? My truck was feeling lethargic lately, so I did the usual tune-up; plugs, wires, cap, air filter. Turns out the tranny fluid was a quart low! Is there any reason to suspect any other drivetrain problems unrelated to the engine that may be affecting performance?

Just saying thinking outside the box can be helpful sometimes. Anyway, good luck finding the problem and fixing it.

--
1982 242 GLT 245k mi: 1985 245 205k mi.

It's an M47 5 speed, and has the same gear ratios, with the exception of 5th, and the same rear axle ratio, as the 740 I'm mentally comparing it to. The clutch isn't slipping, the gearbox is quiet and shifts easily---nothing to suggest anything is wrong in the drivetrain.

The snorkel does not make any diff .I had removed all that stuff 2 yr back but it does not add much.
Did you try a bottle of STP and run it at high rpms (4-5 k ) for 20-30 minutes just to clearup.
Regards

I hope that I did not send a message to the effect that you should modify the snorkel. I simply stated that while I had the intake system apart, I had noticed that the snorkel appeared to be restrictive when compared to the rest of the intake system. I elected to only do away with the heat stove portion of the air cleaner, and not modify the snorkel. I'm not a trained person in the field of fluid dynamics, but it seem to be pure common sense that a restriction of that magnitude would impede performance. I understand that harmonics and pressure wave length and a venturi effect also comes into play. For me, it was enough for those who are far more conversant in the lore of the Brick to say leave it alone. I haven't checked my 0-60 time since I modified the heat flapper on mine (don't have an hourglass). I was not looking to improve the performance at any rate, I was just trying to not kill off another expensive AMM sensor.

Bill

You didn't tell me to modify the snorkel. You merely put an idea in my head, and when I looked at the snorkel, I agreed with your observation, so I pulled it off to see if it would make a difference. I thought it might have, but since I didn't do a series of timed before and after tests, I can't be sure of it. I'm going to put it back on tomorrow, and see if the car seems slower than it was today.

I'm not trying to increase performance beyond stock, just get it back to what it should be, which is the equal of my previous car, an 88 745 with the same engine, manual transmission, and rear axle ratio. By all rights, the 240 should actually be a bit quicker, as it weighs 150-200 lbs less.

I found the airbox from the 740 and measured it. The hot air intake is......48mm in diameter, so maybe that's not it after all.

Tomorrow I'll try it with the vertical part of the snorkel back ON and see it it loses any power.

Ran into a power problem with my 780 Turbo right after I got the car ... on the way home from North Carolina to Nova Scotia with it ... somewhere around New York City there was a noticeable POP and suddenly the car came alive ... it turned out that someone had installed a NON TURBO muffler on and it was so restrictive that it really cut down on the power ..The POP was the side seam of the muffler splitting. When I got home I installed a Magna Flow 14"flow through muffler and it works great now ... The noise isn't a factor either because the Turbo really cuts down on the exhaust note... I could probably have gotten away with just running a straight pipe and nobody would have noticed .. certainly it would not have been as noisy as the usual rice rocket.

Brett

--
Brett Sutherland & the 1.5 million mile 122 CANADIAN --- WINDSOR, Nova Scotia the birthplace of HOCKEY www.ecvintagevolvo.com

Any chance your cat or exhaust is clogged? Is the mixture definitely OK? Good cap/rotor/wires/plugs? Was the battery disconnected before the "snorkel free" test run? :-)

The design of the snorkel (and the intake overall) is in part influenced by the "sound", with it removed, the intake is noticeably louder. Another important consideration is that, yes the throttle body is is larger in diameter than the tip of the snorkel, but you have to then subtract the "profile" of the throttle plate from the X-sectional area of the throttle body itself. So, under nearly all throttle positions (except near or at WOT) the "effective" diameter of the T-body isn't really more than that of the the snorkel.

Despite statements to the contrary, IMHO there's not too much room for improvement in the 240 intake unless replace all the way from the tip of the snorkel to the cylinder head itself.

-Ryan



--

Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars
Buckeye Volvo Club

I don't think the exhaust is obstructed---it just doesn't feel like it somehow. The cat is original (unless it was replaced, long ago, with a genuine Volvo part) and the rest of the exhaust is Bosal and looks like new. Not sure about the mixture---don't have an exhaust gas analyzer to test it with, but it makes no visible smoke, and doesn't even have much of a smell. Bosch cap and rotor, Bougicord wires, NGK BP6ES plugs, all of which look even newer than the mufflers. The battery was NOT disconnected before the snorkel-less run.

I really can't believe that the snorkel is really your problem:

1) Eextensive and oft repeated discussions on this forum have verified (some by engineers with actual empirical measurements of pressure gradients) that the intake (up to the throttle body) offers negligible restriction to the flow of air, given the moderate air flow requirements of a 2.3 liter engine. Any real restriction is at the throttle body and beyond (i.e., the intake manifold).

2) Only relying on the simple diamete measurements you made can be misleading. Any reasonably well engineered intake (and exhaust, as well) system is tuned to optimize airflow, and this tuning would include the dimensions (i.e., lengths) of the component parts -- such tuning includes figuring the standing waves created in the components. Occasionally, changing these lengths (as you did by shortening the snorkel) can actually create flat spots or underpowered portions along the rpm range when the standing waves create interference patterns or do not fit the components.

3) And lastly, the snorkel is designed with an opening pointing backwards (opening facing the radiator/bulkhead, rather than facing forward) to prevent a serious rainstorm from dumping water directly into the mouth of the snorkel.

I think you should look for other solutions, such as a clogged catalytic converter, etc.

As I mentioned in the original post in this thread, I did observe that the snorkel appears to be well designed from the point of view of keeping water and debris out of the airbox, and as I mentioned in the follow-up, I plan to reinstall it tomorrow and see if I notice any difference in the way the car runs.

If you are suggesting the snorkel as designed by the manufacturer, actually limited your engine performance, I say keep looking for a real problem.