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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 12-19-2008, 01:40 PM   #1
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Default Quick question regarding injectors and boost

I have a 92 w/ greddy kit. I am either grabbing some 1.8 injectors ($75) or used 370cc RC injectors (~$200) tomorrow. I have the stock fuel pump. If I'm at stock greddy boost now, and want to get a few more psi, is it pointless to throw in the 1.8 injectors since they're only like 25cc higher? Or would that be enough to eventually work with 12 psi or so? Also - Is there any way to adjust the wastegate arm to get more boost? Sorry if these are noobish questions, and if there are already threads on this, I tried finding them.
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Old 12-19-2008, 01:51 PM   #2
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screw the 1.8's and step upto at least the 370's (Assuming you have some way to make them idle...I dunno how self-adjustable the 1.6 ECU is. I don't see the 1.8 injectors letting you do 12psi on any turbo safely.

you can put a helper spring on the wastegate flapper -or- get an adjustable rod, or make an adjustable rod but why go through the trouble when you can get a good MBC for like $10?

Edit: If you're running an FMU..especially on a stock pump I'd be very careful/concerned upping the boost.
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Old 12-19-2008, 01:59 PM   #3
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Okay so before upping the boost I should get a bipes or something similar first? And if I get the 370's, install the bipes first. Any probably the fuel pump then also, correct? And by MBC... you mean manual boost controller? Could you link me to a good one online? I read some people have issues with some manuals. What do you mean by FMU?
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Old 12-19-2008, 02:11 PM   #4
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Quote:
Originally Posted by linuxbox View Post
I have a 92 w/ greddy kit. I am either grabbing some 1.8 injectors ($75) or used 370cc RC injectors (~$200) tomorrow. I have the stock fuel pump. If I'm at stock greddy boost now, and want to get a few more psi, is it pointless to throw in the 1.8 injectors since they're only like 25cc higher? Or would that be enough to eventually work with 12 psi or so? Also - Is there any way to adjust the wastegate arm to get more boost? Sorry if these are noobish questions, and if there are already threads on this, I tried finding them.
How are you planning on idling the injectors? I thought the green tops (320cc?) were about the largest the stock ECU could handle. Hell w/ the supras my car was running rich as hell in boost. How about you scrap all that, and spend the money on the megasquirt now before wasting your money on injectors you will ultimately sell for 440s or larger in the future? Don't spend the money on bandaids when you will ultimately buy a MS in the future most likely anyway.
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Old 12-19-2008, 02:12 PM   #5
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Okay newbsauce that sounds good. Thanks for the advice!
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Old 12-19-2008, 02:14 PM   #6
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id get the 1.8L injectors if im still using a FMU setup.
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Old 12-19-2008, 02:22 PM   #7
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Injectors = 100-200
Pump = 100ish
Bipes = 80? i dunno

For all that..you can get the megasquirt ECU.

I do happen to agree with braineack, though. If your power goals are very modest, then 1.8s and an AFPR will be good for like ...180hp?
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Old 12-19-2008, 02:33 PM   #8
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just save your money and buy big injectors. Mine were $75 + $120 or whatever to clean them.
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Old 12-19-2008, 06:26 PM   #9
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I get the 1.8 injectors, and don't touch an ything else for now, will there be any power difference? Since it can throw more gas in..?
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Old 12-19-2008, 06:49 PM   #10
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Not likely, but it will run a bit richer.
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Old 12-19-2008, 07:26 PM   #11
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Get a wideband.

Then if you're convinced your power goals are modest. Get 1.8 injectors and the proper disk and you might be able to turn up the boost one or 2 more psi.

If you really want more power than that, get an IC, a MS and real injectors.

Money on a greddy is best spent on a better downpipe though.
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Old 12-19-2008, 07:31 PM   #12
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I had my buddy throw in a custom exhaust for me, and he started it 2.25 inches from the turbo back, so I am good on the downpipe.
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Old 12-19-2008, 08:12 PM   #13
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ok dude... dont listen to anyone.

what you do is:
- stop spending money
- save money
- save some more
- save even more
- go full out with engine build, upgrade to super 16g, throw in some 650s, get aem ecu, cops conversion, 3" turbo -> back, throw 20psi on that turbo while dyno-tuning, and enjoy your upgrade from 150whp to 300-320whp
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Old 12-19-2008, 08:14 PM   #14
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do it once and do it right. dont kid yourself with "modest goals"... eventually (pretty soon actually) you will want to get more power out of it.
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Old 12-19-2008, 08:16 PM   #15
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With regards to mechanically controlling fuel, there are several variables as it pertains to a Miata.

Injector size, ~0 fuel pressure, rate of rise, fuel pump capacity.

The stock ECU on a 1.6 has been show to adequately idle up to 330cc injectors, with some slight fiddling to the idle mixture screw and flapper door spring. You could probably idle much higher injectors by swapping to a fully adjustable aftermarket fuel pressure regulator that removes the factory FPR on the fuel rail. If you could lower fuel pressures at idle vaccum, you could run a larger injector.

When using an FMU/AFPR on a return-style fuel system, the key variables are the fuel pressure setting at ~0 and the rate of rise. The Greddy/Vortech FMU can not adjust ~0 pressure... you're stuck at what you get. You have some finite adjustability with the rate-of-rise by swapping in different sized discs. 6:1 8:1 10:1 12:1... basically, for every PSI of boost, the FMU will raise fuel pressure accordingly... 1psi boost= XX more fuel psi. The FMU will raise fuel pressure only as much as the stock fuel pump can put out.

If you've got your ~0 fuel pressure at say 40psi, and running a 12:1 disc, at 4psi, the fuel pump will be asked to deliver 48psi extra of fuel. The stock fuel pump is limited to 80psi on a good day. A Walbro 190lph will flow 130+psi of fuel pressure. When you exceed the limits of your pump and continue to add boost, you run lean. Lean=Boom.

Corky says (and I can back this up with personal experience) that you will blow your factory fuel lines before you reach the pressure limits of the injectors... they can take a lot of pressure. I ran 130psi of fuel pressure through 1.8injectors for about 6 months before I got a fuel pressure gauge and saw for myself. I was boosting 14psi through a DSM T25 and getting decent AFR's.

Your absolute best bet for power is decent engine management and scrapping mechanical fuel control all together. If you're going to hold strong with the Vortech, NEVER EVER EVER ride in a car with an aftermarket ECU. You'll be pissed that you wasted all the money on bandaids and will have to un-do your hacking of the factory wiring harness where you spliced in the Bipes and 02Clamp, and swap injectors yet again, and realize the Walbro you bought is complete overkill now when you're finally pissed at 15mpg, shitty driveability, slow spool, etc... and buy a good ECU.

Megasquirts pop up used in the Classifieds all the time. In the end, buying new parts, a MS and supporting hardware is a little over $1k.
MS PnP: $700 (cheaper if you have somebody build you one... WAY CHEAP if you build it yourself)
IAT/EBC: $50
Injectors: $100-$200
Wideband: $200

I see Link ECU's all the time as well for even cheaper. There are a dozen popular piggybacks that work very well up into the low 200whp range that you can search for and that are also very popular.

My advice (If I understand correctly that you have an essentially BONE STOCK Greddy kit with the exception of a slightly larger DP) is leave the boost alone for now.

1) Invest in an intercooler. A CXRacing core and universal pipe kit, plus Bosch OEM BOV, 1" T-coupler, 3ft of 1" radiator hose, 1" brass barb... call it $250. You can't turn up the boost without cooling the intake charge.

2) Purchase a wideband 02 sensor. The LC1 is $200 or less anywhere.

3) ACT HD clutch... the group buy is your ticket. You will not find them cheaper than $300 ever again.

4) Megasquirt+Injectors. Do the homework. It's easy. You can be rolling for well under $500.

With the above setup, you're ready to explore the limits of the stock differential. 10psi to keep things simple... that should see you at 200whp even. When you blow the dif, get a Torsen (budget $800), turn up to 15psi and explore the limits of the motor. When you blow the motor, get some 949 rods, ceramic coat the stock pistons, have somebody spend a couple hours on the head... call it $2500. When you're tired of that car, sell it in the classifieds, buy a '99, and start over. That's what I did.
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Old 12-19-2008, 08:25 PM   #16
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Haha wow, thanks guys! I really appreciate your time / advice.
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