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Old 12-02-2008, 10:38 PM   #1
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Default RC 440s VS rx7 550's which and why?

Im going to have to upgrade my rx7 460cc injectors once i get this turbo bolted on and i was wondering which set would be "better" and why?

They will be on a built 1.9L that will never see anything past 300whp.
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Old 12-02-2008, 10:44 PM   #2
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I'd run the 560s. Run more injector than you'll need. Staying away from maxing them out = lower failure chance typically.
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Old 12-03-2008, 04:44 AM   #3
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but arent the RC440s better?
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Old 12-03-2008, 08:56 AM   #4
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The RCs are better injectors but you are gonna need more fuel pressure to approach 300hp. So an AFPR might be in order with the 440s.

TurboTim does run them and makes 290rwhp but runs the 255lph pump.
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Old 12-03-2008, 12:50 PM   #5
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Quote:
Originally Posted by paul View Post

TurboTim does run them and makes 290rwhp but runs the 255lph pump.
thats the info i was looking for, thanks.

Paul, what duty cycle are you seeing with your rx7 550s at the 300whp range?
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Old 12-03-2008, 01:18 PM   #6
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77.5 max DC when i dyno'd at 310hp at 16.8psi @ 7173rpm

80.6 max at 17.99psi @ 7146rpm on the street earlier that day.

I run the 190lph HP pump with a dual feed vishnu rail if that makes any difference to ya.



66 max DC on my other miata with rx7 460s making 233hp at 14.5psi @ 7048rpm with a 190lph HP and Vortech 6:1
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Old 12-03-2008, 01:32 PM   #7
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Snowboarder,one thing you should really consider is a dual feed fuel rail if your going to be running in that hp range.

last thing you need is the stock fuel rail being the weakest link in the fuel system.
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Old 12-03-2008, 01:40 PM   #8
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Quote:
Originally Posted by spike View Post
Snowboarder,one thing you should really consider is a dual feed fuel rail if your going to be running in that hp range.

last thing you need is the stock fuel rail being the weakest link in the fuel system.
How so? What's "weak" about it?
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Old 12-03-2008, 01:52 PM   #9
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How so? What's "weak" about it?
The lack of volume of fuel the stock rail holds and it's a single feed.
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Old 12-03-2008, 02:14 PM   #10
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Quote:
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The lack of volume of fuel the stock rail holds and it's a single feed.
The rail surely has some volume as it has a bore and length. Agreed it's a single feed. Any reason why a single feed rail is bad? Would it happen to be from flow losses across the rail causing a drop in pressure? If so, where would this drop in pressure occur? How much of a loss are we talking about? 1 PSI? 0.1 PSI? Less? What difference in AFR's will this pressure difference cause? Have you ANY evidence whatsoever that there is a problem with the factory fuel rail?
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Old 12-03-2008, 02:23 PM   #11
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I have Mark @ M-tuneds duel feed for a bit of safety.

As far as my fueling system goes. It looks like the rx7 550s are what i should be looking for, my 460s were fine with my 1.6L around the 200 hp range but they surely wont hold up at or around the 300hp range. Is the stock fuel pump going to be enough or is that something that should get changed out too?

Fueling system goes as follows
MSPNP
M-tuned duel feed rail
Stock fuel pump- Is it enough?
currently 460's but will probably go to 550s

Shooting for the 300 whp range
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Old 12-03-2008, 02:34 PM   #12
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I'd upgrade pumps just so it has a new fuel pump.
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Old 12-03-2008, 03:08 PM   #13
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Quote:
Originally Posted by patsmx5 View Post
The rail surely has some volume as it has a bore and length. Agreed it's a single feed. Any reason why a single feed rail is bad? Would it happen to be from flow losses across the rail causing a drop in pressure? If so, where would this drop in pressure occur? How much of a loss are we talking about? 1 PSI? 0.1 PSI? Less? What difference in AFR's will this pressure difference cause? Have you ANY evidence whatsoever that there is a problem with the factory fuel rail?
Not going to get into to much detail,all I can say is,a bigger aftermarket dual feed fuel rail works.

I have installed 3 aftermarket rails,all three miatas with them installed ran smoother,had better idle and the fuel pressure gauge was rock solid(before the rail,the gauge needle was all over the place).Two of the miatas were able to run more timing during the trip back to the dyno.

I'm not a engineer,or a very technical type of guy,but what I do know from experience is,they work and I'm sticking with that.
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Old 12-03-2008, 08:50 PM   #14
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I've had RX7 injectors and RC injectors. The RC are hands down better because they atomize fuel better.
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Old 12-03-2008, 10:54 PM   #15
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Quote:
Originally Posted by patsmx5 View Post
I'd upgrade pumps just so it has a new fuel pump.
+ 1.

New fuel pump can make all the difference in the world. Mine started to get noticeably weaker 2 weeks before dyno day. I had to keep adding fuel to the VE table to maintain my AFRs. Then 1 week before dyno day it got 10x worse. I installed another lower mileage factory pump till my new Walbro came in and even that made quite a difference over what the original pump was doing even months before. My new VE table was calling for so much less fuel now. Just goes to show that the pump does get weak well before it ***** itself.
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Old 12-07-2008, 08:52 PM   #16
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That might explain why my car gets lean in the cold temps. The pump may be getting weak. I just installed another one durring the spark failure, but haven't been able to test it yet. Hopefully it will be up and running next week.
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Old 12-08-2008, 12:11 AM   #17
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My plans are to go with rx7 550s and my stock fuel pump with 110k on it. Ill see how that goes and if im needing more fuel ill look into an upgraded fuel pump.

As far as fuel pumps go, is any pump a direct PNP? I see on various sites that there are "universal" fuel pumps. Just wondering if any of you guys had any insight on it while i await for my parts.
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Old 12-08-2008, 12:25 AM   #18
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the walbro 190lph is as direct pnp as you are gonna get for a 1.6
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Old 12-08-2008, 01:49 AM   #19
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Quote:
Originally Posted by paul View Post
the walbro 190lph is as direct pnp as you are gonna get for a 1.6
The stock fuel pump assembly needs to be modded a little on the 1.6 in order for the Walbro 190 lph to fit.
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Old 12-08-2008, 04:36 AM   #20
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Quote:
Originally Posted by spike View Post
The stock fuel pump assembly needs to be modded a little on the 1.6 in order for the Walbro 190 lph to fit.
Ive did a bit of searching and am yet to come across what exactly needs to be modified. If its a bit of soldering, cutting and splicing wires that no big deal. Any links of info would be greatly appreciated.
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