bling bits

[F1 LOTUS]

[quote author=Candles link=board=boost;num=1112345970;start=15#19 date=05/05/05 at 23:59:00]My Bailey DV30 is definitely open at other times than 'lift off.'  At idle I think it might even be open slightly due to the plenum vacuum.  When I installed it, I didn't initially recirculate it, and whilst fiddling around, I watched the piston whilst opening the throttle and there is some 'breathing' through it.  This was my main reason for connecting it to the airbox.<br><br>Candles.[/quote]<br><br>Well would you jolly well mind getting back under there and disconnecting it then whupping the throttle open to see what happens? If not for me do it for Stef [smiley=1poke.gif]  (high five Doug ;D)

[Candles]

[quote author=Brian_MDB link=board=boost;num=1112345970;start=15#20 date=05/06/05 at 00:18:17] jolly well mind getting back under there and disconnecting it [/quote]<br><br>I see the US contingent are learning some proper English.  Will it be, "Cor blimey guvnor!" Next?  Having said that, I don't know what; "whupping" means  ;D.<br><br>With the vacuum hose disconnected, the piston will be sucked shut under rapid throttle openings, and it it will be assisted by the spring in staying shut.  When the boost comes on, the pressure will push open the piston against the spring, wasting the pressure to air as there will be no balancing pressure from the plenum side.<br><br>What you are striving to acheive (I think) is a mechanism to allow the free passage of ambient air to the plenum under high vacuum situations without the inherent drag of the intake tract, including the turbo.  You then want it to close as boost pressure is developed.  The end result would be the quick throttle response of an N/A, with the boost of a turbo as the revs and time increase.  Is that right?<br><br>If that is right then so far I'm not confused..... <br><br>If the above is right, then I would imagine the flow required to make a difference would be large, i.e. a large, rapidly responding volume of fresh air.  This would probably be best acheived by a reed valve as mentioned above, acting in a large pipe from the filtered side of the airbox to the intake plenum.  The BOV/Dump valve (whatever you call it) function would still be required as this has to open when there is pressure in the intake tract, but unwanted pressure.<br><br>So, your idea is to combine the functions of the two as a recirculating dump valve is the same kind of hardware as the reed valve set-up I mention above?  Well I think it is a good one.  All it needs to do is:<br><br>Pressure in plenum << intake tract: Open valve<br>Pressure in plenum ~= or > intake tract: Close valve<br><br>I'm starting to confuse myself now about which bits are more or less pressure than anywhere else, but I'm wondering if it would be most effective having the breathing part engine-side of the throttle butterfly and the dump valve part on the intake side.  I'm sure this would mess up loads of things though, not to mention the brake servo!<br><br>Now confused  [smiley=damaged.gif]<br><br>Candles.

[Darren]

[quote author=Candles link=board=boost;num=1112345970;start=15#19 date=05/05/05 at 23:59:00]My Bailey DV30 is definitely open at other times than 'lift off.'  At idle I think it might even be open slightly due to the plenum vacuum. [/quote]<br><br>Both my Bailey DV24 & Stratmosphere valves were/are open at idle. <br><br>So do I take it that it should be closed ? If so, should I think about changing the spring in the Dump Valve ?<br><br>[quote author=Candles link=board=boost;num=1112345970;start=15#22 date=05/06/05 at 02:22:21]I see the US contingent are learning some proper English.  Will it be, "Cor blimey guvnor!" Next?  Having said that, I don't know what; "whupping" means  ;D.[/quote]<br>Candles, that'll be because he is English  ;D, he just lives over the pond  ;).<br><br>Darren<br>~~~~~<br>

[F1 LOTUS]

You guys <br>Cor blimey Darren yerve only gone an blown me perishing cover and make no mistake <br>Funnily enough the guys at work do call me 'Guv' and wish me 'Tally ho pip pip' along with liberal use of 'cor blimey' <br><br>Candles...head-nail-nail-head regarding the N/A low end response, I'm sure the turbo engine should be able to respond similar to the N/A at low revs (not that I've driven one)? Have any of you guys tried a side by side Turbo vs N/A rolling drag race? My stock Elans off-boost / low RPM throttle response really does feel choked until the revs get above 3000 RPM especially in a 3rd gear situation?<br><br>I'm not sure a dual purpose BOV is the way to go from the descriptions I'm hearing that it opens on the overrun (when the main throttle is closed), reed valves are nice and simple I'm just not sure what levels of boost they could withstand, Yamaha used them on their Turbo XJ650 motorcycle in the 80's and I think Alfa flirted with reeds too? I actually bought a reed block to give this a try but I haven't gotten (oops!) around to fab'ing this into the top pipe...:-[<br>So what is everybody elses car like when you're at 1500 RPM third gear and you floor the throttle, do you have time to do the Times crossword and write to the editor before you see 3500RPM :-/<br>Cheerio ;D

[Doug]

[quote author=Brian_MDB link=board=boost;num=1112345970;start=15#24 date=05/06/05 at 12:58:43]So what is everybody elses car like when you're at 1500 RPM third gear and you floor the throttle, do you have time to do the Times crossword and write to the editor before you see 3500RPM :-/<br>Cheerio ;D[/quote]<br>hell, who cares how long that takes; it's got a shifter--just drop it in first or second and go like shite!!  ;D

[F1 LOTUS]

[quote author=Doug link=board=boost;num=1112345970;start=15#25 date=05/06/05 at 14:03:59]<br>hell, who cares how long that takes; it's got a shifter--just drop it in first or second and go like shite!!  ;D[/quote]<br><br>And just how long does that take after you've put down your starbucks and swapped hands with the cell phone

[John_W]

[quote author=Brian_MDB link=board=boost;num=1112345970;start=15#24 date=05/06/05 at 12:58:43]<br>So what is everybody elses car like when you're at 1500 RPM third gear and you floor the throttle, do you have time to do the Times crossword and write to the editor before you see 3500RPM :-/ [/quote]<br>Brian,<br>Whilst concurring with the above sentiments expressed by Doug and Rob vis-a-vis selecting a lower gear, I just happen to have a graph showing that it takes 4.8 seconds on an SE. ::)<br><br><br><br>These data were a by-product of some Mountain chip road-testing. They show that the boost cuts in around 3000 RPM, above which the various chips and exhaust sizes differentiate themselves. * However  below 3000 RPM they're all exactly the same. :-/<br><br>Moral? Stay above 3000 RPM if you want the Elan to perform. (But you all knew that already, didn't you? )<br><br>John  ;)   <br><br>* Edited to point out (before somebody says "there's not much difference between the chips") that I make these statements based on more data than are shown here. What's on the graph are just the few datasets which start at about 20 mph; the chip/exhaust benefits above 3000 RPM are shown up better by more appropriate datasets.

[F1 LOTUS]

[quote author=Rob-C link=board=boost;num=1112345970;start=15#27 date=05/06/05 at 15:15:40]Starbucks, cellphone, you may jest, but I've had near misses due to dumbass drivers doing both. Today.<br><br>(Note my savvy use of US-style English in the term, "dumbass" there) <br><br>If you're at 1500 RPM in third, you're in the *wrong* gear! Even more so if you try flooring it in this gear as a way to accelerate!<br><br>Third is good for 60 - 95 MPH in my experience. In fact it's the ideal gear on the motorway, for p*ssing off drivers of more exotic motors, because you can get a really rapid turbo response at these speeds.<br><br> <br><br><br><br><br>[/quote]<br><br>"... in the *wrong* gear!"<br>Exactly! On those odd occasions where you find yourself wrong footed I feel our 1600cc engine should have a far far better throttle response than it has, unfortunately most of my driving is in stop-start urban traffic and perhaps this is why I'm more sensitive to the problem? A couple of times I've been driving little sh1tbox rental cars (Toyota Echo and a Fiat ?) with small revvy engines and their initial throttle response seems sharper than the Elans ???<br><br>I can accept some turbo-lag as a precursor to getting into the big-fun zone but when the turbo is actually restricting the engine or holding it back this seems to be horribly inefficient (very un-Lotus-like) and it would be nice to do something about it?<br><br>"...Even more so if you try flooring it in this gear..." Yeah, I agree and I try to drive such that the throttle is not too far ahead of the engine, the only time I really put my foot to the floor is as a baseline for elanscan runs but it's not the best way to make progress.<br><br>John, thanks for adding the graph, it might be interesting to compare a N/A against this to see what potential there maybe below 3500RPM?<br><br>

[Nige]

I believe I'm correct in saying that the engine in the SE/S2 is not as simple as an NA engine with a turbo stuck on.  The NA engine runsa higher compression ratio , has different valve timing (I assume different cam profiles as well) and produces its peak power at significantly higher revs (130 BHP @ 7200RPM) than the turbo.  I suggest that this all indicates that the NA whilst ultimately less powerful and with less torque than a turbo (and I think torque is what really matters hear) has an advantage up until the point the turbo begins to develop boost.<br><br>Whilst shortening the air path to the engine when off boost may well be of some benefit, it won't do anything about the lower compression ration and valve timing which may be more critical.<br><br>Nige

[Doug]

yeah, just drive a clemo with the electric supercharger/hairdryer option   ;D

[Nige]

Ah, but then you would have to lower the compression ratio and probably play around with the valve timing to avoid detonation problems, doh!  ;)<br><br>Nige

[F1 LOTUS]

You're right about the CR and there's nothing we can do about that but the valve timing in the turbo engine is probably less radical than the N/A and better for low RPM power? :-/

[F1 LOTUS]

[quote author=Rob-C link=board=boost;num=1112345970;start=30#34 date=05/07/05 at 13:45:52]I reckon the answer to all your problems is a Clemo with nitrous  ;D <br><br>Or an Elise.<br><br>[/quote]<br><br>If only this were true... :'( ...:-/... ... Yeah! Everything's b-r-i-l-l-i-a-n-t ;D