Guest Bill_Boro Posted November 13, 2008 Share Posted November 13, 2008 I am installing a low boost super charger (2-4 psi) ahead of the throttle body on my '89 Reatta. Does any body know if the map sensor and throttle body will have any problems? For example, will the positive manifold pressure confuse tpi computer? Also, are there any other issues that I should keep an eye on with this relatively low boost?Thanks for your input! Link to comment Share on other sites More sharing options...
jonlabree Posted November 13, 2008 Share Posted November 13, 2008 Yes, Yes and Yes. First you must overcome the vacuum and then add the boost. Your throttle body must be pressurized so that you don't lose the boost out the throttle bore also you will be blowing back down all of your vacuum lines to all of controls that use it. Link to comment Share on other sites More sharing options...
2seater Posted November 13, 2008 Share Posted November 13, 2008 A few psi will probably be okay. The vacuum modulator on the transmission can handle up to 6 psi of positive pressure according to what I have found but I do use a cheeck valve that vents to atmosphere when under boost. The vacuum to the heater controls inside the car have a check valve to hold vacuum when the engine is off or under full throttle, so it simple blocks the boost. The same is true of the cruise control vacuum reservoir. The pcv valve is actually a crude check valve, that works fairly well. If you are adding more than a few psi of boost, like I have, I added a check valve from an old power brake booster to be sure it seals. It is a pain to fit that in the goofy placement of the stock valve. The vacuum to the fuel pressure regulator will need to sense the boost anyway to increase fuel pressure, so that should be left connected as stock. The last line is the fresh air vent tube to the forward valve cover for the pcv system and that must be relocated to the inlet side of whatever compressor system you are using, or it can be left open to atmosphere with an inlet filter if need be. The MAF and TPS don't care about the boost at those low levels. There is no MAP sensor. My experience has shown that the MAF reading will max. out @ 4-5 psi of boost and the injectors will be marginal, although you may be okay if you raise the base fuel pressure with an adjustable regulator. Watch the readings in the diagnostics and whatch carefully for knock. Good luck. Link to comment Share on other sites More sharing options...
jonlabree Posted November 13, 2008 Share Posted November 13, 2008 He's talking about applying the boost BEFORE the throttle body. That affects the throttle body and the vacuum lines from it. Like the fuel canister for instance. Link to comment Share on other sites More sharing options...
padgett Posted November 13, 2008 Share Posted November 13, 2008 Keep in mind that the stock 89 MAF sensor/programming tops out at 170 g/s. Supercharged engines extend this range. Link to comment Share on other sites More sharing options...
2seater Posted November 14, 2008 Share Posted November 14, 2008 Yup, forgot about the charcoal canister. I don't know what effect the positive pressure would have since mine was removed for a fenderwell air intake. I would guess the valve on top has a check valve function but I don't know if true or not. He wants to do a blow through setup which is the same as mine, although I run twice the boost. The N/A system already operates at atmospheric pressure and he just wants to add 25%-30% more, which isn't a lot. I am not promoting any particular option for supercharging, as any partially developed system will have its weaknesses. Swapping in a complete L67 has its attraction, since it is a fully developed system, but it all depends on what you want to do. Sometimes it's just to answer the question; "what if?", not because it is practical. F14's first experiment actually went very well and exceeded almost all expectations. The weak link was the transmission, not the engine, and the trans. was already high miles. Link to comment Share on other sites More sharing options...
FAA BillyT. Posted November 14, 2008 Share Posted November 14, 2008 What's up with this low boost supercharger? What does it look like-etc? Can you supply info and pictures via this discussion board? Link to comment Share on other sites More sharing options...
Guest Bill_Boro Posted November 14, 2008 Share Posted November 14, 2008 Paget, 170g/s is about 290 acfm at standard temp and pressure. That seems a bit low. What are the latter models rated at?Also 2seater is there a thread on F-14's "experiment"?Thanks Link to comment Share on other sites More sharing options...
padgett Posted November 14, 2008 Share Posted November 14, 2008 Not really, don't forgeet it is only a 231 cid engine, shifts under 4800 rpm, and torque peaks at 2000 rpm. Figuring .85 VE at 4800 that is a max of 270 CFM which is just about where the MAF maxes for a "C" engine. It really has a short profile/low lift cam designed for low RPM torque. My 88 pulls a mild overpass type grade smoothly at 1275 rpm in lockup.I believe the N/A "L" and Series II engines have a larger intake flow area (L-36 is rated at 205 hp AFAIR)but have never measured them. Link to comment Share on other sites More sharing options...
2seater Posted November 14, 2008 Share Posted November 14, 2008 The cfm requirement is a lot lower than you might imagine as Padgett pointed out. I think it is actually lower as the volumetric efficiency is lower at 5k rpm, somewhere around 65%-70%, per information I received from Vortech many years ago. It takes just a few pounds of boost to reach the maximum flow rate capability of the MAF. It will flow a lot more, the system simply cannot read it and you have to go by dead reckoning. GM did a pretty good of matching components. The MAF and throttle body air flow rates are very similar although the screen does reduce flow, but you need to keep it in most cases. Try a PM for Master Philip (F14). He had a very extensive writeup. Link to comment Share on other sites More sharing options...
padgett Posted November 15, 2008 Share Posted November 15, 2008 and if you flow more in, consider the out. Some time ago I found that the exhaust "collector" connection is very restrictive but can be opened up. Link to comment Share on other sites More sharing options...
Guest Greg Ross Posted November 15, 2008 Share Posted November 15, 2008 There was an extremely well written Swap "How To" on this website;http://forums.motorswap.org/viewforum.php?f=6&sid=93b61119349f02cc4a1989cbbe326a45I had a bit of a look around this afternoon but could not find it. This guy was a "Pro" and put together a very detailed record c/w photos. Link to comment Share on other sites More sharing options...
Ronnie Posted November 15, 2008 Share Posted November 15, 2008 http://forums.motorswap.org/viewtopic.php?t=1396&sid=33913f1b3078dc35ddd5aa1ad44886a3 Link to comment Share on other sites More sharing options...
Guest Greg Ross Posted November 15, 2008 Share Posted November 15, 2008 Thanks Ronnie,This is the Thread I was looking for. Darth Fiero is thorough and obviously this was not his first Rodeo! Link to comment Share on other sites More sharing options...
Guest Bill_Boro Posted November 15, 2008 Share Posted November 15, 2008 By dead reckoning do you mean that the top end fuel/air ratio must be manually readjusted via increasaed fuel pressure and/or higher gpm injectors? Does anybody know if the computer/O2 sensor still provides feed back to adjust the injector on time even if the MAP sensor maxes out? Link to comment Share on other sites More sharing options...
jonlabree Posted November 16, 2008 Share Posted November 16, 2008 The computer can be modified for almost any "Improvements" Link to comment Share on other sites More sharing options...
Guest F14CRAZY Posted November 16, 2008 Share Posted November 16, 2008 I'm a little late to this chat...Bill: how's is your supercharger being powered? Exhaust driven or electric? Or mechanically?Its been ages since I've been deep into this, please excuse me guys if I'm a bit rusty... At the airflow rate mentioned the ECM cannot recognize the signal from the MAF. The ECM relies on programmed tables, it's airflow vs. RPM vs. load. Load is determined by the TPS if i remember right. The three are figured together and the ECM judges what to do with the injectors.Without the reading from the MAF at higher power levels, things can be inaccurate. However, a good tuner and some time on a dyno can get it to be just fine. I've used Ryan of Sinister Performance in Fort Wayne, IN...gmtuners.com. He'll be happy to discuss things with you Link to comment Share on other sites More sharing options...
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