kalium99 Posted July 17, 2002 Share Posted July 17, 2002 Hi, just wondering if Triple twin barrell 40mm Mikunis will show any advantage over a holley 650 in a relatively high (400hp) turbo setup ? In regards to volume of flow, and distribution of A/F to the cylinders Cheers Ray PS On an Inline 6 (4.3 Litre) Quote Link to comment Share on other sites More sharing options...
Mike C Posted July 17, 2002 Share Posted July 17, 2002 Is this a draw throught or blow through setup? Blow through is extremely difficult because the need to preasure seal the carb by mounting it (or them) in an enclosure. So I will assume it is a draw through. It will be MUCH easier to do this with the single carb rather than the triples, but I have seen a turbo setup that used a pair of SU mounted right next to each other on a home-built intake. IMO you are whizzing uphill into a wind trying to do the turbo thing with a carb. The OEM manufacturers never managed to get carb'ed turbo engines to be much to speak of (think 60's and 70's, even early 80's as turbo cars were real POS usually). EFI and electronic engine controls change this drastically. If I were you, I'd go EFI or wouldn't even waste my time with the turbo thing. Quote Link to comment Share on other sites More sharing options...
DAW Posted July 17, 2002 Share Posted July 17, 2002 I agree, with a factory bolt-on f.i. and ECCS setup available why use a carb for a turbo? You could do the triple sidedraft (6 throttle plates) approach by using f.i. throttle bodies on a triple manifold with a plenum (or weld injector bungs onto the manifold and alter the triple carbs by removing the venturies and epoxy-shutting the feed holes in the carb barrels to make them function as throttle bodies). The benefit of the mutiple throttle plates would be in great throttle response but overall, for a street-driven car it's probably not worth the hassle vs a stock f.i. setup. DAW Quote Link to comment Share on other sites More sharing options...
kalium99 Posted July 18, 2002 Author Share Posted July 18, 2002 From what I have seen, read and heard, sealing a Holley or a MIkuni is not that hard...well not as hard as an SU anyway (apparently). There are so many examples of good Blow-thru (and even draw-thru) which are making great power without FI. There are a couple of 9sec Centura's running Hemi 265 and a blow-thru setups in Australia which just goes to show. EFI would be ultimately better of course...but at what price? Too much me thinks. Here is an interesting conversation RE blowthur/drawthru vs FI that I found on a mopar board. Sorry for the length, but I think its an interesting read. Turbo charged engines using carburettors are prone to be unreliable --- Easy statement to make. examples please? Not properly setting up a carb will lead to trouble. People know when they make changes to an EFI engien that they will need to be tuned/remapped. The same people think a carb will magically be right to go as is.... -- Due to the large range of parameters i.e., rev range, throttle opening, ignition requirements, load conditions etc, it is not possible to properly control the boost, mixture and ignition requirements through the whole rev range under all conditions using a carburettor and conventional ignition system -- In short, that's why there are things like idle circuits, main circuits, air correctors, power valves (or metering rods). Carbs are designed to operate under a wide variety of conditions. They can be sorted. ABSOLUTE WORSE CASE SCENARIO - you ensure that it is spot on for full throttle full boost and you lose a little bit of fuel economy (and believe me if you have the time and the motivation, you can address this too) If you get into really big boost - like mid to high 20s psi wise, it does get to the point where you will be compromising on off boost fuelling, but not many people go this high anyway - even the EFI guys. I'd suggest that if you are heading toward that much boost, off boost running wouldn't probably be a big concern to you - so any compromise would be irrelevant. There have been a few factory turbo charged and superchaged cars that have been carburettored. They definitely got it right. The fastest 6 cylinder torana is Simon Pimms black one. It is drawthrough carbed. There is a very quick centura that was (not sure of it's status in 2002) running a drawthrough holley. -- This can lead to lean a mixture and to much ignition under particular circumstances resulting in a destroyed engine -- You can do this with an EFI car too - they aren't magical and will suffer just as much if improperly sorted. This is the sort of scare tactics that people selling EFI stuff push - so they can profit. There is no profit in carbs. If they told you you could make the same power for around 1/4 the cost, you would feel pretty ripped off. Too much timing or too little fuel and any car (EFI or carbed) will have a short life. The key here is to set things up properly regardless of which path you follow. Don't get me wrong. EFI is good. If your car already has it then by all means use it. If cost is a concern and you don't already have efi, carbs are a definite option. -- In order to get satisfactory results from a turbocharged engine it is necessary to use a good EFI management system. -- satisfactory? so running low to mid 9 second quartermiles is unsatisfactory is it? It's (or it should be) blatantly obvious that most people who are derogatory of carbs wouldn't know a thing about them and their function, and how to tune them. -- A. Purchase an EFI engine such as the Z18 turbo, FJ20 turbo or SR 20 turbo. These will all fit into the 1600. (They all require an Engineers Certificate). --- cost - $10,000? -- B. Fit a turbo and aftermarket EFI system such as the Motec to you 1600 or an L20B engine. Each of these options will cost six or seven thousand dollars. The simplest would be A. -- 7 grand to net the same result as roughly $1000.... I have some beach front property for sale in Alice Springs. -- C. Another option is to fit an L20B with big port head, flat top pistons, cam and 40mm Webers or Dellorto carb's. This combination will give 0 to 100km in around 7 seconds and excellent reliability and fuel economy for less than half the cost of a turbo engine. -- I've been pretty nice up till this. What a wanker seriously. Twin carbed and high compression (even high compression and EFI) will not get anything near the power of a carbed turbo engine - not even close. Reliability? that is complete horseshit. Turbo engines don't have to rev any higher than stock ones. to get more power normally aspirated you have to move the torque peak up the rev range. more rpm = less engine life. This guy has some serious holes in his knowledge. There are guys on the blowthruturbo list who have been using the same short block for 20 years - no bull. fuel economy suffers big time with hot cammed cars, because you have to be reving higher to be in their power band. At lower rpms they are decidedly less efficient than their stock cammed counterparts - and this affects fuel economy greatly. You might also need to go to a lower geared diff to take advantage of it. A turbo engine goes fine with stock gearing and for that matter you can even go higher in the diff gears without any loss in performance. half the cost. I am sick to death of posting costings and full run downs of how tos. If it cost more than $1500 to turbo your engine, it would be unusual at the very least, unless it is specifically aimed at a lightning quick 1/4 mile time. To get a sub 7 second 0-100 - definitely you could do it for less than $1500. It would also be far more friendly at lower rpms..... As for an EFI versus carbed 'plug', about a year or so ago a subject came up in aus.cars where a guy was wanting to seel turbo kits for cars for around $1000. I asked if it was for carb only (since you couldn't possibly do it on an EFI car for that). HE said 'no its for EFI cars - their computers woudl automatically add extra fuel. and furthermore, people with carbed cars woudl be better spending their hard earned cash on EFI first!" Now obviously the guy was clueless as to EFI stuff - and was completely incorrect on that front. But I also suggested that the spending on EFI would be ridiculous. I mentioned that AT BEST efi on a normally aspirated car would add 5-10% power. Even the most bodgy homebrew carbed turbo could give a 50% (or more) gain in power. Julian Edgar, editor of autospeed.com, who is one of the most 'pro technology' guys around posted in response to the original poster, and his post was pretty much making the same points as i did (albeit it without murdering the english language like I do). That doesn't mean to say he thought carbs were superior, but in that comparison - EFI N/A or carbed turbo - the carbed turbo option was the clear winner. There are too many people who have successfully run carbed turbos for it to be impossible. The thing to always keep at the forefront is to make sure the carb is set up properly. Ignition systems are the same. You can get an old distributor to provide an almost identical curve. If you get one with a dual diaphragm vacuum advance cannister you can even have boost retard. Without this, you hav eto set the mechanical advance (and initial) so that it will max at a setting that won't result in detonation. You still get vacuum advance at part throttle for decent economy. The one and only place you miss out is at part throttle at the point wehre there is zero vacuum and zero boost. This would be the situation where you have a little less than optimal advance. I should be quick to point out that this makes up less than 1% of driving time. With a dual diaphragm vac cannister though, even this minor issue will not occur. I have links somewhere for a turbocharged L series engine if you want them. Even with an 'agricultural' drawthrough setup it went quite well. ok here comes the brag - I started my apprenticeship in a galaxy far far away at a place that was at the time the only authorised Lotus service centre in Aus. My memory is not perfect, but I do remember one esprit in particular that used to be transported in from interstate regularly. They were blowthrough carbed. The last year I was there was just when GM more or less did a 'takeover' . The lotus for that year got GM efi, and the corvette of that year got a head using lotus' experience. (I should point out that at this time lotus the car maker and lotus the formula one team had absolutely no ties. I don't know when how or if they were ever tied together, but around 1990 they were totally separate). The lotus was quicker with efi - but not dramatically. The corvette on the other hand was like night and day. This in and of itself should illustrate that as long as fuelling is addressed, the specific method has no significant bearing on power potential, and breathing is what it's all about. Similarly, the new (now no longer being made) 5 litre holden motors really got a powerup when they went EFI. Most people said it was proof positive of the power gains of EFI. nonsense. The gains are 99% from the new heads that they came out with. The proof of this is how fast some 308 holdens have gone with these heads and a carb. These heads flow more standard than the most extensively ported pre EFI head. If EFI was the real contributer here, there is no way known there would have been any carb manifolds ever produced for these heads. Fact is the manifolds are available, and are being used.. Case closed. I am using these examples to try and bring together an engine you mentioned - the Z18 (and I am probably getting the numbers and letters wrong). AFAIK from posts on various forums this is more or less an L18 engine with a new head. Or at the very least the head can be fitted to the L series engines. Again the point here being that the better flowing head is the desirable bit, not specifically that it came in an EFI package. Other cars off the top of my head. There is a lancia that was blowthrough supercharged with a weber 34/34 dmtt. There was also a factory blowthrough turbo MG metro - basically a mini engined and gearboxed ford laser clone. I happen to have more than one complete sets of these (if I play with it, it's a good bet I turbocharge it) A couple of things which came to mind today (when I was not hot under the collar). The various mailing lists I am currently on, in particular the blowthruturbo list always emphasises inlet manifold selection/modification/construction. The focus here is on equal mixture distribution to all cylinders. Fail to address this and you will definitely run into trouble. I bring this up because the list has a track record of concentrating on things like this - i.e. getting it right. The other tid-bit. I happen to live a stones throw from a big name in turbocharging in Melbourne. I get to see (just from my daily commuting) just how long some of their 'flagships' - cars which have featured in magazines etc spend actually running and how much tiem is spent in the workshop. You would have to think that they would put the maximum time and resources into these cars in particular, since they would result in the most business coming in. Yet they can't manage to get their own cars to hold together. Does this mean that they are muppets (well maybe but probably not)? Does it mean that EFI is inferior? nope not at all. For the record the only area or yardstick where EFI is consistently inferior is in terms of hp per dollar - it is almost impossible for it to compete. So what does it mean? For the most part it means that any car that is competitive, or setting records is running on the limit. If you made an engine and it could produce lets say 500bhp reliably. All well and good for 99% of us. For someone chasing a record? Well he or she would have to go further pushing out 550 or maybe 600. And things will break. Then you find a way to get it to hold together a little better, and obviously if you don't someone else will, so you have to push the output higher again. This sort of thing will happen whether it's carbed or EFI and is the 'catch' or drawback of pushing the envelope. As a side issue, Bigdodgedave (who knows me personally away from the moparmarket forum) can attest to some of the horror stories that people I know and/or those know to my circle of friends - concerning certain turbo 'specialists'. I am talking about guys who have spent literally thousands on rebuilt engines, the works, EFI intercooling etc - and have literally nothing but scrap metal to show for it. Despite it all being done 'the right way' . One of these cases is so completely outrageous the owner is negotiating with a car magazine for the rights to the story. He has given up all hope of the vendor rectifying the problems, and is tossing up what he could likely win in a civil action versus what is being offered for the story.... Point being you can spend all that and still be no better (or worse) off. If you wish to save a hell of a lot of money (and let it be said that 'If I had unlimited funds, or won tattslotto or whatever, every turbo project or car I owned would be EFI - there would be no reason not to. While budget constraints are still the go, none of them will be.) and still get excellent performance (and this certainly covers all but the most extreme street/strip or strip only projects - which can still be carbed, but will cost a bit more) then by all means get on the www.yahoogroups.com homepage, sign on blowthruturbo (which has the most extensive carb sorting/modification/tuning data pool) and have a long look through the archives. There is 100% definitely enough there to cover almost any project you can come up with. It will give you an excellent foundation to build on. If there is still some stuff unanswered, post a question to the list (or even email me or Dave) - the info is not far away. As I keep harping, the real 'advantage' of retaining a carb is the cost factor. It allows even students on a tight budget to put together a really decent streeter. You aren't going to beat a WRX with $50,000 spent on top of the purchase, but you could definitely take on the std ones for a couple of grand tops. (pray for a labor federal government and you can probably get a $20,000 arts grant for performance art - turboing your car and doing burnouts! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 18, 2002 Share Posted July 18, 2002 I know Turbo Tom had a single carbed turbo that was supposed to make 400hp on an L28. Quote Link to comment Share on other sites More sharing options...
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