Clifton Posted February 22, 2008 Share Posted February 22, 2008 Well i might need a bigger Turbo however i would like a flat curve, what you describe would make more top end and less lag. Ill keep you guys updated! this weekend ill header wrap the spaghetti incident. The SC will give you the bottom end torque. If the hotside on the turbo is small enough to make boost at 1500, it will kill the top end with excessive back pressure, torque would fall off sooner if it's being choked, plus you are already using a little power to drive the sc. Bob Norwood did one with a 1mz (I think) Toyota engine, it was a few years back (maybe 5) but it was in Turbo magazine. They had dyno graphs too. I'm not trying to down your project, it's pretty cool. Quote Link to comment Share on other sites More sharing options...
frank280zx Posted February 25, 2008 Author Share Posted February 25, 2008 The SC will give you the bottom end torque. If the hotside on the turbo is small enough to make boost at 1500, it will kill the top end with excessive back pressure, torque would fall off sooner if it's being choked, plus you are already using a little power to drive the sc. Bob Norwood did one with a 1mz (I think) Toyota engine, it was a few years back (maybe 5) but it was in Turbo magazine. They had dyno graphs too. I'm not trying to down your project, it's pretty cool. Clifton, don't worry i have the same concern! however i bought the turbo before i decided to twin charge.. however lets test and see.. otherwise ill go bigger (like a holset orso) But what would you guys suggest ? turbo wise a hx55 ? as a 35 would be small on this set up when wanting real big numbers! Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted February 25, 2008 Share Posted February 25, 2008 An HX40 would be perfect. It would come on hard boost around 3800-4000+ RPMS on a 2.8L. It came on an 8.3 liter diesel... Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 25, 2008 Share Posted February 25, 2008 An HX40 would be perfect. It would come on hard boost around 3800-4000+ RPMS on a 2.8L. It came on an 8.3 liter diesel... On a 2.8L that is NORMALLY ASPIRATED! On a 2.8L that has a 1.5 Compression Ratio Blower on the front, it's exhaust flow will be more like a 4.2 Liter... Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 25, 2008 Share Posted February 25, 2008 I thought that the point of the S/C was to make up for the lag of the bigger turbo? That way you can have the S/C making low RPM boost while the turbo makes higher RPM boost where the S/C is inefficient. The "Lag" ARGH! The higher boost threshold? The supercharger is a full time consideration to allow for more efficient compression. If you mechanically compress at a 1.5 CR, then your turbo which normally would need to flow efficiently in the 3.2 C.R map will not be needed, and you can optimize a turbo for 1.5 CR (which has a much wider application band) and still have the same terminal power, with far more lower end torque. What you are mixing up is a supercharger that acts as a supplementary device, meant to fill the powerband below boost threshold, and a turbo that is sized to provide power with a LOW boost threshold using a LOWER Compression Ratio. This engine will not be running to 9000 rpms. It is limited in that respect. The Supercharger makes for an engine that in effect is a 4.2 L, and the turbo is supplementing that for midrange and top end polishing of the power curve. They are being designed to work concurrently not sequentially! There is a BIG difference in the application. While the larger compressor section may be needed to support the Supercharger's goals, the ultimate design will probably use a very large wastegate to bypass flow the turbine wheel to keep speeds under control, as you are using hte turbo with a boost threshold in the low 2000 rpm range! That's off-idle with the right cam, especially on a serious track car. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted February 26, 2008 Share Posted February 26, 2008 Tony, or anyone. What kind of heat issues is Frank looking at? Would it need to be intercooled? Or is the supercharger not working that hard? I guess I understand that alot has to deal with how much boost each stage is running. I was hope for a little more insight on the heat stuffs. Quote Link to comment Share on other sites More sharing options...
frank280zx Posted February 26, 2008 Author Share Posted February 26, 2008 Tony, or anyone. What kind of heat issues is Frank looking at? Would it need to be intercooled? Or is the supercharger not working that hard? I guess I understand that alot has to deal with how much boost each stage is running. I was hope for a little more insight on the heat stuffs. It will be inter cooled between the charger and the plenum, if that proves not to be sufficient i can choose to do so between each stage, but with 7psi from the turbo i doubt ill need that Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted February 26, 2008 Share Posted February 26, 2008 Tony, There are guys using HX40's on their 302 Ford V8's all the way up to 383 SBC's... I am plety sure it is big enough for Frank's "4.2L" motor. Frank, I can't wait to see this engine up and running! Be sure to make videos!! Quote Link to comment Share on other sites More sharing options...
Gareth Posted February 26, 2008 Share Posted February 26, 2008 Frank, you wrote that the SC will be fed by the turbo, which means that the piping will have to be routed to the back of the SC. If so, then how are you planning to route the piping, around the engine or over the valve cover? Another thing is, aren't you afraid that the very hot air compressed by the turbo will break the SC somehow? I've always thought that SCs are vulnerable to hot air for some reason... Quote Link to comment Share on other sites More sharing options...
frank280zx Posted February 27, 2008 Author Share Posted February 27, 2008 Frank, you wrote that the SC will be fed by the turbo, which means that the piping will have to be routed to the back of the SC. If so, then how are you planning to route the piping, around the engine or over the valve cover? Another thing is, aren't you afraid that the very hot air compressed by the turbo will break the SC somehow? I've always thought that SC's are vulnerable to hot air for some reason... Ill route over the valve cover the way it seems now, and as im only pumping 7 PSI im not to worried about the SC ... but time will tell (btw this is not a wet charger and from the top of my head those suffer from heat more) Quote Link to comment Share on other sites More sharing options...
BurnoutZ Posted July 27, 2008 Share Posted July 27, 2008 What ever happend to this project? Has it progressed? Quote Link to comment Share on other sites More sharing options...
Xander Posted July 27, 2008 Share Posted July 27, 2008 Frank destroyed the engine when street tuning megasquirt. The engine was fighting us all the way and in the end Frank got fed up with the l28 and is now installing a BMW V8. When we finally got this thing running and we were doing some tuning frank had a lot of electrical issues and the engine would not run cleanly to redline. He got pissed of and destroyed the engine. He was really pissed of and wanted an engine that would be easy to drop in, has a reliable 400hp and not give him any headaches. So I told him: Get a chevy V8 (crate)engine. You can buy the engine mounts and all the R&D has already been done. He agreed with me for a change!. So he bought a BMW 4.4 liter V8 His build is documented in another thread and to be honest it is actually progressing nicely. Quote Link to comment Share on other sites More sharing options...
BurnoutZ Posted July 28, 2008 Share Posted July 28, 2008 Hmm... does he have any pictures of how he routed the tubing? I think he shouldve tried working out the bugs... Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 2, 2008 Share Posted August 2, 2008 Hmm... does he have any pictures of how he routed the tubing? I think he shouldve tried working out the bugs... When the engine blows up 2X and screws you out of two paid track days...you start wanting something you can actually drive! It's easy to make someone else's decision for them, if it's not you hammering till 3AM every night after work trying to make the next track deadline. The superturbo will simply go into his street car, something he doesn't need to have running by any date. His plans are already working toward the readily available BMW tuning components in his homeland. Chipsets for the ECU, Supercharger... You got to understand, Frank (er, his surrogate shipper-parts goopher in the USA, me) spent more than $256 in shipping costs in a single week to get some bearings, and then some lash pads overnighted. Frankly, the parts are hard to come by, and I believe his choice of powerplants...for where he is...is a FAR better choice for what the intended use of the vehicle will be. He has less into the BMW V8 swap than he has in broken components from the first L-Engine Failure. Plus, the engine and transmission is considerably less weight than the setup he took out...as well as being completely behind the front axle line...mid-engined if you will. He wasn't going to get that with the setup he was using. The more he added, the heavier the front end was getting. Not good on a track car without power steering! Quote Link to comment Share on other sites More sharing options...
boardkid280z Posted August 12, 2008 Share Posted August 12, 2008 AAAAAAAAAwwww, so sad to hear about the problems with this project, I was really excited about it Frank and hopefully things will go smoothly in the street car. Keep us up to date on how that goes. Quote Link to comment Share on other sites More sharing options...
frank280zx Posted September 2, 2008 Author Share Posted September 2, 2008 Thanks guys ... Xander and Tony nailed it .. i will finish this.. (dont know when) but on my car that is now still on tony garden .. Just running not wanting more than 250 to the wheels .. i have all the stuff i just need time .. but first the V8 But did you say Chevy Xander ??? guess i missed that part due to backgroundnoise .. http://forums.hybridz.org/showthread.php?t=136195&highlight=BMW+v8 Quote Link to comment Share on other sites More sharing options...
dum-bass Posted September 5, 2008 Share Posted September 5, 2008 Wow! Quote Link to comment Share on other sites More sharing options...
Guest Schlaumberger Posted October 15, 2008 Share Posted October 15, 2008 Tony D, you seem to be mistaken on some of the principals at work in this form of twin charging (it's a different story if you attempt to bypass, and then disable the supercharger). There is no fixed ratio on a roots supercharger. The thing to remember is that a Roots style supercharger is an air pump, and nothing more. It is NOT an air compressor. Yes, air gets compressed often when an M90 is used, but that is more a side effect of it trying to move ever increasing amounts of air into a space that has a very small exit. When the pressure on the intake side of a roots "blower" is less then that on the exit side, heat is generated. The greater the difference, the more heat that gets generated. Yes, there is heat generated by the air being moved, and also through bearing friction, but this is only accounts for maybe 1/3d of the temperature increase. If you take a roots supercharger, and force feed it, to the point that it's intake is say 14psi, and it's spinning at a speed such that it's exhaust (for use of a better word) is also at 14psi (due to intake diameters and such) it is actually doing no more work then just spinning the rotors the same as if it were at idle. This means no heat, and virtually no parasitic drag on the engine. Now what does this means in regards to a turbo charger? You can no use a turbo sized so large, that it would have stalled before. This is because the supercharger is "sucking" enough air, that the flow never reverses which would have caused it to stall. Ideally you want your turbo charger to spool, as the supercharger is nearing the end of it's efficiency range -in the case of the M90; it would be spinning somewhere around 10,000 RPM which would hopefully be somewhere near the middle to two thirds of your car's RPM range. At this point the turbocharger should be flowing enough gasses that it starts to relieve the pressure imbalances on the supercharger. The turbo needs to be sized such that as the supercharger's airflow increases (at this point well beyond it's original operating spec) that the turbo's airflow ALSO increases, but at the same rate. This would make turbo size, and waste gate efficiency a priority (unless you bleed off excess pressure through a Blow off Valve) The only limiting factors to this setup is how fast, the bearings on an M90 can spin before they fail, and how much total pressure the rotor seals can take before they fail. I have not been able to find these answers yet. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 20, 2008 Share Posted October 20, 2008 There is no fixed ratio on a roots supercharger. The thing to remember is that a Roots style supercharger is an air pump, and nothing more. It is NOT an air compressor. Yes, air gets compressed often when an M90 is used, but that is more a side effect of it trying to move ever increasing amounts of air into a space that has a very small exit. When the pressure on the intake side of a roots "blower" is less then that on the exit side, heat is generated. The greater the difference, the more heat that gets generated. Yes, there is heat generated by the air being moved, and also through bearing friction, but this is only accounts for maybe 1/3d of the temperature increase. Those are somewhat incorrect/misleading statements. The roots style blower is an air compressor. This is not open to debate, it's a fact. Semantically if you want to differentiate it as a 'blower' or 'air pump' because it's a single stage application below 15psi discharge pressure that still does not relieve it of conforming to the physical laws regarding compression of gasses (Boyle's Law amongst the primary one coming readily to mind). But 'air pump' is the same thing as 'Air Compressor'. To think otherwise begs questioning who is misunderstanding the application. The reason heat is generated (even through your example) is that the pressure ratio or the 'air pump' or 'air compressor' (pick whatever term you like) goes sky high in a non-bypassed blower. Bearing friction adds nothing to the heat generated to the air stream. Heat added to the airstream is purely a function of the pressure ratio being experienced and the stage compression efficiency at the time of compression. I'm not sure what you are getting at, as most everything you said mirrors exactly what I have discussed. You speak of pushing air through a supercharger as opposed to bypassing around it during some modes of operation...what's the point again? I'm just confused at what you are getting at, or how it differs in any way from what has already been discussed. That the Roots Blower is a variable compression air compressor dependent on inlet and outlet pressures? Goes without saying, but at some point in the design stage you have to pick your ideal tip-speed, and compression ratio, and move outward from those points. Ideally any Roots Style blower is inefficient at a given pressure ratio. You don't see them in 55psi(g) applications much, do you? No, you will see Lysholm Screws, or two-stage centrifugals. Roots Blowers simply don't like 3:1 PR. 1.5:1 and at most 2:1 is their effective, practical limit. With a 7psi turbo pressure into the blower, and shooting for no more than a 1.5 pressure ratio (and designing your drive speeds to be accordingly set to achieve this tip speed/flow number) you would get 17.75 psi(g) out of the blower at the same temperature as you would in standard atmospheric service discharging at 7.25psi through the blower alone. How is that any different than the example you gave? I think I have a pretty good handle on the physics and engineering involved in the prototype design Frank was proposing. I have a little background in this area. If you can get in touch with on of the Ballas up in Buffalo NY, they used to run a shop that rebuilt blowers for the NHRA guys running in the N.E. circuits up and down the east coast, lots of rebuild stuff from BDS and the like. They closed down shop and moved on to other things just because of strain on the families doing all the travelling and long hours associated with the racing season and being in a critical support role. I'm sure he could tell you on any give big blower what is possible. His shop pulled in commercially avaialble blowers and totally reworked the rotors, gave a proprietary coating because the available commercial stuff (even though the casing said one thing) wouldn't hold up to the pressures used in competitive NHRA events. Rotor Flex became an issue as well... Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted October 24, 2008 Share Posted October 24, 2008 Cool............you can actually be one of the few people with a true "intercooler". Quote Link to comment Share on other sites More sharing options...
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