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Mazda 750 Holley blowthrough
My name is Blake and I have a 87 TII I just purchased. I have wanted one since I was 18. It has a 13B - S5 Rotors, 3mm Apex seals, T04 Turbo and was recently rebuilt. It has a Holley 750 double Pumper sitting on top with a Hat to the Turbo (no intercooler).
It was driven off the truck (thankfully it started!) from a 3 day shipment from El Paso and immediately parked. I flooded it the next day, and from reading, realized this was a big no-no to start and quickly park an RX7. The temperatures here are hovering in the 30's so I have avoided trying to start it since. The first day, I pulled the plugs, turned it over for 20 seconds, dryed the plugs, put in a squirt of ATF in each rotor and hooked everything back up. It just spun over (but felt like there was compression) but with not even a sputter. I did hear it run initially the night before (albeit somewhat badly and for a short time). Any tricks to starting one of these beasts? Pump the pedal or no? Starter fluid? CandS said there would be no chokes available for a blow-through so am I just dead until summer I guess? The carb is leaking from the side float bowl, so I may just send it off to CandS for a diagnostic / rebuild. I would love any advice anyone has to offer. |
welcome to the board. :)
https://www.rx7club.com/1st-generati...t-prep-539319/ https://www.rx7club.com/1st-generati...estion-563099/ https://www.rx7club.com/1st-generati...fusion-495375/ https://www.rx7club.com/1st-generati...-help-1050830/ pay attention to posts by wankel=awesome. there are a few other Holley guys that really know their stuff, too, but he's the only one i can think of off hand. |
Originally Posted by blakec123
(Post 11628873)
My name is Blake and I have a 87 TII I just purchased. I have wanted one since I was 18. It has a 13B - S5 Rotors, 3mm Apex seals, T04 Turbo and was recently rebuilt. It has a Holley 750 double Pumper sitting on top with a Hat to the Turbo (no intercooler).
It was driven off the truck (thankfully it started!) from a 3 day shipment from El Paso and immediately parked. I flooded it the next day, and from reading, realized this was a big no-no to start and quickly park an RX7. The temperatures here are hovering in the 30's so I have avoided trying to start it since. The first day, I pulled the plugs, turned it over for 20 seconds, dryed the plugs, put in a squirt of ATF in each rotor and hooked everything back up. It just spun over (but felt like there was compression) but with not even a sputter. I did hear it run initially the night before (albeit somewhat badly and for a short time). Any tricks to starting one of these beasts? Pump the pedal or no? Starter fluid? CandS said there would be no chokes available for a blow-through so am I just dead until summer I guess? The carb is leaking from the side float bowl, so I may just send it off to CandS for a diagnostic / rebuild. I would love any advice anyone has to offer. Pump pedal twice, hold throttle slightly open with foot and keep it running until it idles on its own. As for the leak, try tightening down the 4 bolts holding the bowl on. No need to pay C&S that much money. Look at theturboforums.com plenty of info there. Is this engine ported? I have a 650DP Holley on my blowthrough, works great past 9K, with AFR at 11.3-11.6 at 10psi. |
Originally Posted by ArmyOfOne
(Post 11647511)
Ok here is my blowthrough startup routine Pump pedal twice, hold throttle slightly open with foot and keep it running until it idles on its own. As for the leak, try tightening down the 4 bolts holding the bowl on. No need to pay C&S that much money. Look at theturboforums.com plenty of info there. Is this engine ported? I have a 650DP Holley on my blowthrough, works great past 9K, with AFR at 11.3-11.6 at 10psi.
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You need to find out what the previous hack-job owner who set up that carb did for timing.
Depending on what was done you may be looking at another rebuild shortly once you start driving in boost. Unfortunately there aren't too many options to get a decent drivable timing curve while maintaining safe timing in boost. The only real option (not including using an ECU to control it) is to lock the dizzy at a safe value (about 10 degrees). Which is fine in boost, but terrible for 99% of other driving. If it's just a stock dizzy, then advance will be dangerously high in boost. Honestly, I'd recommend tossing the current fuel/ignition setup into the parts bin where it belongs and setting up a proper standalone EFI system. Yeah, it's an investment, but after which the car will be safe, drive properly, reliable, and start at the first turn of the key. |
Originally Posted by Aaron Cake
(Post 11647666)
You need to find out what the previous hack-job owner who set up that carb did for timing.
Depending on what was done you may be looking at another rebuild shortly once you start driving in boost. Unfortunately there aren't too many options to get a decent drivable timing curve while maintaining safe timing in boost. The only real option (not including using an ECU to control it) is to lock the dizzy at a safe value (about 10 degrees). Which is fine in boost, but terrible for 99% of other driving. If it's just a stock dizzy, then advance will be dangerously high in boost. Honestly, I'd recommend tossing the current fuel/ignition setup into the parts bin where it belongs and setting up a proper standalone EFI system. Yeah, it's an investment, but after which the car will be safe, drive properly, reliable, and start at the first turn of the key. |
Carb + electronic timing
Thanks much Guys!
I'll let you know the first warm day how it works. Good call on tightening the bolts on the Carb - I'll try it. I actually do some automotive electronics. Great call on the ignition timing. I may do an advance box where I can dial in the advance based on boost and RPM. A full up fuel injection box is a pain to do because of the massive amounts of code necessary, but a box that varies ignition with RPM and boost/vacuum is pretty attainable. Should I pull in Throttle position as well... as long as I am building one I might as well get all the inputs that really matter. Blake |
MegaSquirts start at $300 if you have electronics experience and even an ancient MS1 will run the car better than that carb.
If you do build your own ignition box, remember that you have both leading and trailing ignition to deal with and they run different timings. But an "advance box" is ancient technology for 60 year old men putting "blowers" on their muscle cars who still complain about that "new fangled fuel injector thingie". It may sound like I'm being harsh but it is only because of modern EFI systems that we are able to build high HP turbo rotarys that are reliable in the long term. Fuel and ignition control is critical in an engine that is not tolerant of detonation. |
I just bought my Megasquirt MSIIIx for $675 pre assembled, plus a $75 harness.
Can control way more injector banks than I need, FC ignition, 8 custom programmable outputs, USB connectivity, auto self-tuning for both fuel and spark, closed loop o2..... The list goes on. |
I hear you loud and clear on the fuel injection. I was the Chief Engineer at Hypertech for 7 years and we pretty much worked hacking OEM fuel injection 24/7. I have great respect for it and it sure beats the hell out of a carb. However doing a proper EFI setup requires a considerable time investment, and total cost would likely run more than I have in the car. Plumbing, wiring, hooking up sensors, tuning etc is a real job. I have followed the Megasquirt for years. In college, my team did a Natural Gas conversion for a turbocharged GM truck using an Electromotive EFI setup with a modified gas grill regulator instead of injectors. What a bunch of work that was...
If I end up keeping the car, I am sure fuel injection is in the long term plan, however I'll take a stab at seeing if I can at least get it running around with the cobbled together carb setup that is on it. The car would look at home on the 'Road Warrior' so the Carb setup will fit right in :) |
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