Alphabettispaghetti
Club Member
steering rack is going to make a right mess of your battery
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Anyone running open trumpets / velocity stacks?
- Thread starter AliK
- Start date
steering rack is going to make a right mess of your battery
Alphabettispaghetti
Club Member
what reason was that for? was your car the wrong colour?
Alphabettispaghetti
Club Member
sorry I meant brake M/C etc.
I do recall the PMAC / Skidell dream team doing a list of rolling road work on this topic and it transpired that open trumpets suffered with reflected waves off the side of the engine bay. If I recall they said the late Mr F style air box was the best way forward for power.
But I guess loosing 5-10 bhp may be worth the sound effects of open trumpets if the car is not about ultimate power.
But I guess loosing 5-10 bhp may be worth the sound effects of open trumpets if the car is not about ultimate power.
Albrecht
Well-Known Forum User
R&D is interesting and I guess it is useful when chasing ultimate tenths, but when dealing with 50+ year old cars you can easily end up attempting to count how many angels are dancing on the head of a pin.
The idea of reflected waves off the side of the engine bay makes my eyes glaze over. Presumably a strut brace would also affect a couple of cylinders more than others? How about a bank of tiny spring-loaded baffles to 'catch' the waves and bounce them back at the inlets? A bit like the roof of the Albert Hall? No, maybe not...
Meanwhile, back in 1970:
Albrecht
Well-Known Forum User
here's a quick analysis of those 70's rebound waves....
albeit a very non-scientific one...
Analysis readout:
Cylinder 1 = 0.0008% power reduction due to proximity of fuel filter.
Cylinder 2 = 0.01% power reduction due to proximity of strut tower.
Cylinder 3 = Ditto.
Cylinder 4 = Full power on every second Saturday of the month!
Cylinder 5 = Ditto.
Cylinder 6 = Oh dear, it's the clutch master cylinder...
Farmer42
Club Member
I ran open 75mm trumpets on my twin SUs and the car ran better than with the OEM airbox but that is orange so perhaps it was the wrong colour.
I bought a couple of trumpet filters from the US to fit to the front (see pic) and have not had any problems. However I have now switched to K&N deep filters and will be dropping smaller trumpets inside. I am very risk averse when it comes to my car so that is why I switched.
I bought a couple of trumpet filters from the US to fit to the front (see pic) and have not had any problems. However I have now switched to K&N deep filters and will be dropping smaller trumpets inside. I am very risk averse when it comes to my car so that is why I switched.
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Paul_S
Club Member
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Well Mr T, I’m not sure about the definition of spitting back, but all engines have reversion - more so those with longer duration / overlap cams.
Case in point, after running mine with open carbs for my web cam and tuning antics, the paint opposite the front carb on the strut tower (much like my webcam screen and head torch on the other carb) has fuel marks / discolouration on it.
I would suggest that it’s not just the “spitting back” but more so the shockwaves coming back up the inlet tract that may be contributing to the foam filters breaking up.
DCOEs “spit back” more for this reason than SUs as there isn’t the carb piston in the middle restricting them as much and the inlet path is a straight line to the ports. This isn’t like a misfire due to timing issues with the cam or ignition where it makes a popping noise through the carbs. I know that noise well - remember when my timing was c.300 degrees advanced and blew apart my silencer in the process of trying to start the car? (My 123 ignition installation where I stupidly trusted the no.1 mark on the Beru cap).
My A4’s throttle body that is quite a long way around the corner from the valves was completely black and gummed up on the rear side (and that is a modern TFSI engine) - next time you take your SUs off, look at the black soot on the back of the butterflies or the rear of the pistons - ever wondered where that’s coming from!?
Case in point, after running mine with open carbs for my web cam and tuning antics, the paint opposite the front carb on the strut tower (much like my webcam screen and head torch on the other carb) has fuel marks / discolouration on it.
I would suggest that it’s not just the “spitting back” but more so the shockwaves coming back up the inlet tract that may be contributing to the foam filters breaking up.
DCOEs “spit back” more for this reason than SUs as there isn’t the carb piston in the middle restricting them as much and the inlet path is a straight line to the ports. This isn’t like a misfire due to timing issues with the cam or ignition where it makes a popping noise through the carbs. I know that noise well - remember when my timing was c.300 degrees advanced and blew apart my silencer in the process of trying to start the car? (My 123 ignition installation where I stupidly trusted the no.1 mark on the Beru cap).
My A4’s throttle body that is quite a long way around the corner from the valves was completely black and gummed up on the rear side (and that is a modern TFSI engine) - next time you take your SUs off, look at the black soot on the back of the butterflies or the rear of the pistons - ever wondered where that’s coming from!?
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peter_s
Club Member
I was visiting one of the top engine builders yesterday in Sweden. I asked the question about running without arifilters, and he only said: "Stupid idea... ask X (a shared friend) what can happen if you run without an airfilter".
He have blown a whole engine. I'm buying an airbox for my trumpets...
He have blown a whole engine. I'm buying an airbox for my trumpets...
Running without a filter is tempting because it's easy, sounds good (not for quiet trackdays though) and looks uncluttered - however would you be happy to buy a secondhand expensive modern car that the PO was running without a filter? I know that's a hypothetical situation but what would it tell you about the owner?