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Stock S5 TII with REVII exhaust, 1.5 or 1.7??

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Old 07-21-16, 06:47 PM
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Stock S5 TII with REVII exhaust, 1.5 or 1.7??

I'm hoping this is the right place to ask this question.. it feels like I've read all the threads out there and I still don't know whats best for my car!!

So, I have an '89 S5 TII Vert, currently its stock engine wise aside from a drop in filter.

I've got an RB Rev II turbo back exhaust which is nearly ready to go on.

To help monitor things, I've got an AEM boost gauge and an AEM wide band O2 sensor ready to fit


Now the bit I'm stuck on. The RB website says I must use an FCD with this exhaust, so I went and bought a HKS FCD that came up locally.


But after doing a bit more reading into how an FCD works, I'm not so sure its really the best thing for my car. The Rtek 1.5 seems to give the FCD function but with some other bits that make it sound better than just an FCD on its own

So I was reasonably happy I'd go with a 1.5, job done. But now after reading a few more threads, I'm wondering if I need to be adding more fuelling in terms of a better pump and 720cc secondaries and looking at a Rtek 1.7 instead?


Can anyone help me choose which path to go down??!! Any help is greatly appreciated

Pic of my car for interest

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Old 07-22-16, 01:16 AM
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Are you planning on modifying your car any further? If so, then the 1.7 might be a better option. The reason you need an FCD in the first place (which an FCD is a bandaid at best) is the free flowing exhaust allows the turbo to reach higher boost pressure. That being said, you WILL NEED new 720cc injectors with the 1.7.

The 1.5 is basically a drop in upgrade that complements the Racing Beat exhaust nicely. You really won't be able to run much more boost over stock or anything fancy, but it will get the job done. Consider your options and your limits. If you are splurging on the aftermarket gauges and what not, it may be worth it to drop in new 720cc injectors, a new fuel pump, and crank the boost up to 10-12 PSI.

The Rteks are great in that they are reliable and use factory pieces. The downside is the limitation of the factory computer. This is all up to you, but if you plan on leaving the car alone, go with the 1.5
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Old 07-22-16, 12:02 PM
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Hmm modifying further... the age old question haha

I'm not planning to go mad with it as I use it daily and would like to keep that usability. But I guess it would be nice to have a bit of headroom to play with in the future if I do want to push the boost a little further

So that makes the 1.7 with 720cc injectors (and presumably an FD or aftermarket pump) seem like the way to go

Can always start with that, then get a boost controller I guess to raise it in the future if needs be?
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Old 07-22-16, 12:31 PM
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Look at the Aeromotive Stealth pumps. high quality pumps that are also quiet.
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Old 07-23-16, 09:17 PM
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The correct way to do this is remove the turbo, port the wastegate so boost can be controlled, and then use an electronic or manual boost controller to get the boost where you want it. Letting it creep up to whatever PSI is hacky, and possibly unsafe.

If you are going to the trouble of 720cc injector installation, I suggest pulling the turbo and doing that work at the same time.

Plus, once the turbo is ported, you can go on and do other traditional light mods such as intake and exhaust without fear.

Sidenote: A full voltage stealth fuel pump will probably overrun the fuel pressure regulator as well (ahhh the slippery slope). You might want a good adjustable FPR, but you do have to plumb it somehow.

It's hard to do light power mods to these cars because lots of different (but small) systems need upgrading to support the boost.
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Old 07-23-16, 10:51 PM
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^ Great points here. I am planning on the Stealth pump, but I'm going to run an Aeromotive FPR as well. I keep forgetting that the T2 has a fuel pump resistor.
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Old 07-25-16, 01:16 PM
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Originally Posted by ColinShark View Post
The correct way to do this is remove the turbo, port the wastegate so boost can be controlled, and then use an electronic or manual boost controller to get the boost where you want it. Letting it creep up to whatever PSI is hacky, and possibly unsafe.

If you are going to the trouble of 720cc injector installation, I suggest pulling the turbo and doing that work at the same time.

Plus, once the turbo is ported, you can go on and do other traditional light mods such as intake and exhaust without fear.

Sidenote: A full voltage stealth fuel pump will probably overrun the fuel pressure regulator as well (ahhh the slippery slope). You might want a good adjustable FPR, but you do have to plumb it somehow.

It's hard to do light power mods to these cars because lots of different (but small) systems need upgrading to support the boost.
Ah yeah wastegate porting was another thing that I'd read much about but people seemed to be doing it more on the S4 turbos than the S5's but if it makes an improvement then I'm not against porting mine

I'll have to do a bit more reading into how far to port it out


That last point is exactly what I'm finding, lots of these mods are all intertwined!

FPR wasn't one I'd considered to be honest, another thing to add to the list
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Old 12-20-16, 06:03 PM
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Damn been a long time since I posted in this thread!

In the end I fitted the Rtek 1.7, Aeromotive Stealth pump and 720cc injectors. I haven't had a chance to port the wastegate yet but I did just about manage to get the car running.

I put it all back together in a bit of a rush as I needed the car running so I could move house lol so I think theres an air leak as it idles around 2.5k but it does drive although I kept it off boost

Something I have noticed though is that when you turn the key to ignition (without starting) theres quite a lot of clicking coming from the engine bay, sounds like relays? Is this a normal/common thing with uprated fuel pumps etc?

I'm still running the stock FPR
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Old 12-24-16, 12:58 PM
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Originally Posted by adam73bgt View Post
Something I have noticed though is that when you turn the key to ignition (without starting) theres quite a lot of clicking coming from the engine bay, sounds like relays? Is this a normal/common thing with uprated fuel pumps etc?
No, but it depends on how you wired it. The best way is to use a new circuit (from the battery or alt) to the pump, with a new fuse and a relay that is triggered by the old fuel pump circuit. That way, you get the safety feature where the pump only runs when there is ignition + airflow through the AFM.

If you added a new relay to the engine bay, it could be clicking. It shouldn't click repeatedly.
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Old 12-26-16, 03:54 AM
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Its just wired in with the stock wiring at the moment, the clicking does stop when the engine is running though, hmm maybe I'll have to look at running new power to it, although the stock wiring looked in good shape

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Old 03-20-17, 08:29 PM
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I'm about to follow this very same approach, my car does have a down pipe and full exhaust. Is your car a jspec RHD?
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Old 03-21-17, 07:28 AM
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Its a UK spec RHD car, I've been told they do differ slightly from the Japanese spec cars but I'm not sure of the actual differences
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