Ka24e turbo build questions

[S13_MN]

I know there's probably a million threads about kids wanting to turbo their sohc ka but my build needs to be within the next 2 months so I need some questions answered asap.
I know forsure that I need the following:
Turbo
Manifold
Downpipe
Bov
Wastegate w/pipe
Intercooler and piping
255 fuel pump
450cc injectors
Oil catch can
Oil feed and return lines
Gauges
Boost controller
Adjustable fpr

But what else do I need? I plan on running low boost (no more then 10psi) and I'm kind of on a budget. Do I need to get the car tuned? Do I need an safc 2? Or greddys emanage? Or an fmu? Any suggestions will be much appreciated

[pepesilvia]

Here's my 2 cents (because you said you were on a budget):

If you're running low boost you dont need that size injectors, You should go with 370cc injectors from an SR20(you can find used ones for way cheaper than new larger injectors) IF YOU DO upgrade yur injectors than you have to use a tuneable program like e-manage (pretty expensive if yur on a budget and you'll probably need some help tuning it) or you can even use SAFC II (a lot cheaper then e-manage and easier to use). If you stick with the stock injectors and upgrade your fuel pump then you can use an FMU, which is the cheapest option. An FMU will only run you 80-150 bucks and dosent require a tune. (im not sure about the ratio you'd use for SOHC though. depends on boost and size of turbo too)

I would also be weary about running 10psi on SOHC. I would try to stay in the 5-8 range.

Also, if yur gonna buy a cheap turbo manifold, buy a cast iron manifold because they are less susceptible to cracking and overheating the PS reservoir which sits close to the turbo...

Good luck

[S13_MN]

So if I'm running between 5-8psi of boost I can use the stock injectors with an fmu? Also I'm looking at a Garrett gt28 w/ a 7psi internal wastegate.

[S13_MN]

Also do I need an adjustable fpr if I'm running an fmu? And do I NEED a boost controller if I have a 7psi wastegate? I'm new to the turbo scene

[pepesilvia]

Yeah if yur using stock injectors then you can use an FMU. You WILL need an adjustable FPR with the FMU. I would only suggest running an FMU up to 7 psi max. If you plan on running any more boost i would suggest bigger injectors and a tuneable device as opposed to an FMU. The FPR will regulate the fuel from vaccum to 0. The FMU will regulate the fuel from 0-7 psi. An FMU will never perfectly regulate fuel under boost pressure, so when accelerating you will probably run both lean and rich at different times. I would suggest getting a wideband o2 sensor to monitor if yur motor is running lean or rich. I would also suggest buying a Vortech FMU because you can change the fuel ratio (you gotta buy the different ratio inserts though) if you notice that it is running too lean or too rich at times.

[PapaSmurf2k3]

You wont need a boost controller if you plan on just running whatever your wastegate pressure is.

Make sure you buy a downpipe that is made for internally wastegated turbos (you wont need an extra waste gate).

Even at 7psi, you're going to be running a LOT of fuel pressure. With an 8:1 FMU, at 7psi of boost (assuming 40psi base fuel pressure), you're going to see 96psi... which is pretty high.

I'd recommend ponying up and just getting larger injectors and an SAFC.

[S13_MN]

So it's not safe to run an fmu on 7psi of boost? And I know this is a dumb question but I need to remove the stock fpr if I'm getting an adjustable fpr correct?

[pepesilvia]

You wont need a boost controller if you plan on just running whatever your wastegate pressure is.

Make sure you buy a downpipe that is made for internally wastegated turbos (you wont need an extra waste gate).

Even at 7psi, you're going to be running a LOT of fuel pressure. With an 8:1 FMU, at 7psi of boost (assuming 40psi base fuel pressure), you're going to see 96psi... which is pretty high.

I'd recommend ponying up and just getting larger injectors and an SAFC.

^^^ I agree. I went down the "cheap turbo kit route" and I always had problems (fmu stock injectors too) While it is possible to run 7psi, its not recommended. Especially on a single slammer. Also, yes, you have to remove the OEM FPR to install an aftermarket one. Good luck though, those little screws are a PITA to remove so close to the firewall. You might be better off removing the fuel rail entirely.

[S13_MN]

I appreciate the info on the fpr. What kind of issues were you running into? Too lean or too rich?

[PapaSmurf2k3]

cheaping out in general leads to reliability issues, less power, etc.

You can go cheap, but only to a certain extent. At 7psi, you are pushing the limits of going cheap. I think at that level I'd rather see larger injectors with a hacked MAF than an FMU.
Some 370cc injectors and a precision drilled hole will do wonders
Here's a pic of my hacked maf setup that I ran for a while on my Miata while I was between ECUs:

[S13_MN]

So I can get away without a piggy back or an fmu by hacking the maf? Please tell me how if so

[S13_MN]

Btw this only has to last me the summer. I'm rebuilding the motor next winter. So if an fmu with stock injectors will last 3000 miles/ just this summer, that's all I need

[PapaSmurf2k3]

I mean, its tough to rebuild something with a big ol hole in the side of it, but roll the dice however you see fit.

The way a hacked MAF works is that you essentially suck in un-metered air to counter the larger injectors you have in the engine.

So say you have a 2.5" inlet pipe.
Area = pi*r^2
= about 4.9 inches squared.

370cc injectors are about 37% larger than the stock 270cc.
So you'll want to counter-act about 37% of the air that is being metered.
4.9 * .37 = 1.8 square inches needed.
1.8 = pi * r^2
.57 = r^2
r = .75
So theoretically you'll want about a 1.5" diameter hole in your intake pipe after the MAF. Realistically, you should start smaller than that and measure your air fuel ratio and increase the hole size as necessary, or put in an adjustable valve in your bypass circuit there. You want it to run a little richer, so you likely will never get to the 1.5" benchmark.
I think I actually ended up using a .75" tube with a filter on it. Your stock ECU will also compensate to an extent as well.

note- there are many ways to pull off a hacked MAF setup, this is just one of them. It's nowhere near as good as having an SAFC or other electronic fuel management though.

[S13_MN]

Now does the placement of the hole between the maf and the turbo matter or just anywhere?

[PapaSmurf2k3]

I pretty much put it wherever it was convenient for me. I'd keep it away from the edges though.

[pepesilvia]

I mean, its tough to rebuild something with a big ol hole in the side of it, but roll the dice however you see fit.

The way a hacked MAF works is that you essentially suck in un-metered air to counter the larger injectors you have in the engine.

So say you have a 2.5" inlet pipe.
Area = pi*r^2
= about 4.9 inches squared.

370cc injectors are about 37% larger than the stock 270cc.
So you'll want to counter-act about 37% of the air that is being metered.
4.9 * .37 = 1.8 square inches needed.
1.8 = pi * r^2
.57 = r^2
r = .75
So theoretically you'll want about a 1.5" diameter hole in your intake pipe after the MAF. Realistically, you should start smaller than that and measure your air fuel ratio and increase the hole size as necessary, or put in an adjustable valve in your bypass circuit there. You want it to run a little richer, so you likely will never get to the 1.5" benchmark.
I think I actually ended up using a .75" tube with a filter on it. Your stock ECU will also compensate to an extent as well.

note- there are many ways to pull off a hacked MAF setup, this is just one of them. It's nowhere near as good as having an SAFC or other electronic fuel management though.

Wow, now thats interesting... I've never even heard of that... hmmmm it makes sense i guess.

[WDRacing]

Pepesilvia, please don't post links to another forum. That's not cool.

[WDRacing]

Just my .02 here...

You don't need an adjustable FPR if you're using the FMU. Why would you? The stock FPR continues working with or without the FMU installed. The FMU is mounted after the stock FPR and works in conjunction handling all of the on boost fuel demands by ramping up fuel pressure. It does this by basically restricting the return flow, therefore increasing fuel pressure at the injector.

People have been running 8 psi or less with a FMU for years. Works great. If you don't want to invest in a proper ROM tune, then the FMU is the best option.

Stay away from the SAFC and other piggybacks. The FMU is a WAY better option. The piggybacks aren't that cheap and they still require tuning. I've used the hacked MAF, the SAFCII, the ROM tune and gone as far as running entire standalone subinjection systems.

The reasoning behind my opinion is simple. I've seen more poorly running cars than ones that run smoothly when the SAFC or other piggyback is used. The piggyback cars always have stalling issues, idle issues and generally don't run well. I played with mine for a month, with a wideband and I still had the occasional stalling issue. The FMU is cheap, it works and it doesn't require anything from the user as far as tuning goes. If you're new to turbos, you don't want to start by tuning with a piggyback, bad things will happen.

The other reason I shy away from piggybacks is, hello, a real ROM tune can be had for a couple hundred bucks more. This gets you a car that starts and idles like stock and runs like a raped ape under wot. IMHO, it's well worth the extra money. Take my advice, I've been down the DIY as cheaply as possible route before, I'd go with the FMU for under 8 psi or the ROM tune.

The hacked MAF. Not a good idea unless you're experienced with tuning. You'll need a wideband O2 meter, knock meter and adjustable FPR to make it work. When using the hacked MAF, the timing tables are also going to be skewed because of the extra unmetered air. This causes the ecu to run more timing than it would otherwise. More timing on boost is a bad thing. Or at least it can be a bad thing. Which is why I suggested the knock meter.

In short, FMU or ROM tune for fuel management. If you run anymore than 7-8 psi you're going to need to retard your ignition timing. You can do this by retarding the base timing at the distributor, but this will negatively affect your off boost power and fuel economy. The other option is the MSD BTM, which is a MSD ignition box and a remote controller that mounts in the cabin that allows the user to retard the timing while on boost from 0-3 degree's per psi of boost. I used the MSD BTM on my S14, it does a very good job.

Is your car running real well right now? Any leaks, cooling issues etc? A turbo will compound any current problems 10 fold.

You're also going to require the highest octane available from here on out. So 91 or better.

Keep the questions coming, we have a wealth of knowledge in the KAT world.

WD

[pepesilvia]

Pepesilvia, please don't post links to another forum. That's not cool.

Sorry. I didnt even realize, I was just trying to help

[WDRacing]

No worries dude. I didn't think you were out purposely trying to undermine Nico or anything. Just lettin ya know.