wasnt to sure where to put this thread at but here goes.

ok guys i have modded the MS with the duel vr and the car is doing pretty good now.
still havent gotten it to a dyno .
but wanted to see what you all think as to what size injectors i should run for two twin turbos. right now i have 550 primaries and 550 secondaries. i know i need bigger but not to sure on what size? my guess is 850 primary and 1000 secondaries? the turbos are running 7-10 psi each and the motor is getting street ported. is there 1000 injectors that will fit the stock fuel rail? if not where can i get one that will. or do i have to make one from scratch which i dont have a problem in doing so.

any info would be great guys.

 

Personally i would get GSL-SE injectors in the primaries, and put bosch indy blues in the secondaries.

Whats wrong with a normal non-ported 13BT with a GT35R? I really doubt you will make any more practical power with a ported engine and funny mods like that.

 

You really don't want those primaries too much larger than the SE 680/720s. It becomes difficult to get a decent tune at idle and lower load levels like cruise. I would calculate how much total fuel you need from one of the injector size calculators that use projected horsepower and BSFC as inputs. This will get you in the ballpark. I like http://www.rceng.com/technical.aspx as a decent place to start. Do you have compressor maps for your turbos? These can be very handy in seeing whether or where you're going to surge or stall those compressors depending on the projected mass flow. What 2 turbos are you using?

-Mike

 

being the motor runs strong as is now, i would think i could get by with a stock port. but always seeing threads of people blowing up there setup cause of forgetting "needed mods"leads one to think that maybe the porting is always recommended for horse power increases.
WILL the bosch fit stock fuel rails? need more info on that please sir.

i was considering that garrett GT35R as another upgrade option and would seem more doable in my platform. but i would still need to atleast upgrade the secondaries?( im going to look into this one more.)

i was planning on using both my s4 turbo's they both been rebuilt recently and also in the makings of the extra piping for the second turbo. two turbos down here = more bragging rights!!! dont ask lol
i HOPE that the out come is that i get quick boost and both kicking in at about 2500-3000 if both push out 10 psi atleast i can live with that. if i cant do the twins then the other turbo can go to my other turboed project =)

oh BTW my motor is a 88 j spec if that has any lead way?
550 all around.
walbro 255 pump
front mount 2 core
stock fuel rails
red square tops with tab offset on the injectors "came with the Jspec"

 

#1 Regarding required mods. I really can't see what they are talking about for a turbo motor.

you don't need any special clearancing or balancing for 11000rpm
you don't need special apex seals if it doesn't ping
you don't need porting because overlap with a turbo isn't always a good thing

I think the only valid point would be dowel pining or putting studs through the engine, and making sure that your 88 rear iron has the meatiest rib around the oil filter. I've been told that is the weak point. That said I'm sure with a good tune plenty of people have gotten that sort of power without silly mods like that.


Regarding the primary injectors

As far as I know all the top feed rotary injectors are plain old nippon-denso injectors and will go straight in.

Regarding the secondary injectors

As far as I know Bosch 1600cc 'Indy Blues' have 14mm top o-ring and 14mm bottom o-rings when you buy them.

#1 Remove the Top 14mm O ring
#2 Measure the diameter of the rx-7 injectors plastic below its top o-ring grove.
#3 Machine 1600cc injector to match the dimension you just took.
#4 Slip grommet over plastic, put 11mm o-ring in grove

Thats the top now sealing. With the bottom you have to remove the pintle cap and the o-ring, and make it look like the denso injector there. There used to be a website, I will try and find it.

 

thanks for all the input guys.

im going to go with the duel turbo setup i can see it happening for me .the gt35r is out of my price range right now so that will have to be put to rest. .plus since i have the turbos here i want to put them to good use. i have considered going with the 1000 secondaries rather then 1600 the gap seems to far out there versus the primaries.

 

or, the japanese-style injectors off of injector.com are a drop-in (at least my 570 and 1000cc ones were), so you dont need to do any special machining or anything.

For anything over 8000 or 8500 RPM I've heard that you need stronger stationary gears (and maybe the pressed in gears in the rotor too, i'm not sure on this point). Also, you probably won't be making much power up there unless you do some porting for flow, and maybe a little bit later closing for the intake and opening for the exhaust ports (but NO overlap, any overlap with a turbo engine will just result in more internal EGR and less power).

 

Thats not true at all. Low end power suffers, midrange and top end increases. A bridgeport is a perfect example.

 

but with a turbo engine? NA, yea sure, but turbo the exhaust pressure can be much greater than the intake pressure, and if there's overlap, much more of the exhaust gasses will be pushed back into the intake tract, giving you more egr, heating the intake charge, slowing combustion and displacing fresh air and fuel. Now, whether the effects of the extra EGR outweigh the effects of momentum on cramming more charge into the chamber, thats where experimentation and experience come in. I dont have any experience with porting, i can just try to reason these things out.

 

Well, look at it this way.

People make more power with turbo bridge and peripheral engines than with turbo street port engines.

It's not a matter of debate, since people are doing it every day.

Yes, turbo selection/sizing is critical. Exhaust manifold pressure can (and should) be lower than intake manifold pressure. Low overlap engines will also benefit from this proper sizing but they are also more tolerant of a less than optimal setup.

It's just like exhausts on N/A engines. Bridge/peripheral must have free flowing and well-tuned exhausts, so they end up being loud. Street/stock port engines ALSO like having free flowing and well-tuned exhausts... but it's not a massive power killer if they don't have it.

 

Ok, so i guess the advantages of that overlap outweigh the disadvantages, at least at higher RPM.

Doesnt a bridge-port really just increase flow area, but not really change the port timing? It seems that most of the gains to be made would be in flow area, not overlap timing, and overlap is only really necessary when you run out of port-able area elsewhere.

 

Port timing increases dramatically with a bridge port, and it's all on the opening side.

The overlap makes more torque everywhere on the tach, it is not a top end only thing. You lose power at low throttle opening (high pressure difference intake vs. exhaust) but from as low as 2000rpm on up it makes scads more torque. This is why exhaust is critical and especially why turbo sizing is critical!

If you want a peaky high RPM only car then do a huge street port.

 

sorry no updates on this guys its getting cold out here to work on the car so its been on hold =( getting the custom header make dont have pictures yeat. and made all the templates. trying to see how im going to redo the coolant lines to both turbos and also the oil feeder lines again....

 

ToplessFC3sman:
what Impedance is your 1000cc injectors? im trying to figure out which ones i need. the stock 550cc injectors i have are red top and from a 88 j spec motor so i think its a low impedance injectors? anyone know which one is it or a way i can check myself to see where a part number will tell me the impedance on them. i dont want to buy the wrong impedance and have a mix match injectors.

 

the stock 550cc injectors are high impedance.

 

My car originally had the high imp injectors, but I replaced them all with low-imp and drive them with the MS that way without a resistor pack. If you want to mix them with high-imp, then you can get the resistor pack from a pre-87.5 car and wire it in series with the injectors. On the other hand, you can get some pre-87.5 injectors and run the whole thing as low-imp.

 

SOME stock 550cc injectors are high impedance.

Around the middle of the 1987 model year is when they did the switch from low impedance to high impedance. Before that ALL rotaries had low impedance injectors.

So the majority of TII (most S4/all S5) are high impedance but there are quite a few early production models out there that are low impedance. Those are the ones that can take GSL-SE injectors as a straight swap.

Only your ohmmeter knows for sure!

 

mine is 550 high impedance