Need some facts for my turbo...

[racin-type]

I have a 93 240sx with 131,000 miles currently. Did a compression test and all cylinders were about 1-2 psi above the upper limit(179). No idle problems, runs great. Have always thought about turboing my ride, recently been doing alot of research on what i want in my setup. I'm trying to build a turbo engine with the lease amount of "accessories" to save money/headaches. accessories meaning external wastegate, unimportant gauges, fuel pump, ect...

My turbo setup:KA24DE - 7psi maxJGS log manifoldInternally wastegated turbocheap bovcheap intercoolerCustom intercooler/dp piping Straight pipeboost gauge

However i need some questions cleared up before i can move onto the next step.

1)What is the max hp/boost pressure the stock injectors can handle. Related to that is how much can the stock maf handle? 2)Alot of you are using the T3/T04E/B's, however i know those turbos will need extra fuel accessories that i don't want to buy. So i'm limiting myself to about 7psi, the question is what is the simplest fuel setup i can use? Fuel pump or FPR or fuel filter to raise base fuel? AFC with stock fuel setup?3)I've heard great things in the other post about T3's on our engines. Some of you say its too small and winds down towards redline. And that after 11psi its useless. This seems like the right turbo to me. Can i net aleast 225rwhp with this turbo setup?

Haven't been on this forum in the past but now i've found that its one of the greatest resourses. Thanks alot any and all coments opinions are welcome.

[C-Kwik]

1. The stock injectors will start getting lean as soon as 4 psi. A Boost dependent fuel pressure regulator at 7:1 or 8:1 can probablt handle about 6-7 psi if the pump is working well. I can't remember what the S13 MAF limit is.

2. see above.

3. it is achievable with a T3.

[huguetpj]

1. Yes the stock fuel system will start running lean by 4PSI. I have runned the stock fuel setup for about 6 months now, no issues so far. But after going to the dyno I wouldn't recommend it. Already purchased a 7:1 RRFPR as a band aid for now.

1b. From what I've read, the stock MAF limit should be around 10-12PSI. It depends mostly on CFM, so it will vary depending on turbo size and other specs.

[junk240sx]

When people say 'stock fuel system' i assume you guys mean the stock injectors.

Tell me if I'm wrong but I've known people with stock fuel pump running much more boost than that. Rather it's the injectors that would need to be upped. I think that's why many just run sr20det 370cc injectors and a hacked MAF for fuel setup for boosts under 10psi.

[huguetpj]

For me stock fuel system means stock fuel pump, stock injectors and stock fuel press regulator. You might also wanna throw stock MAF into the mix.

And yes. As long as you keep the fuel pressure at stock baseline then the stock fuel pump can take bigger injectors, although I wouldn't use it with anything bigger than 370s. But since a Walbro 255HP can be bought for around $100, why would one want to risk the engine?

[racin-type]

huguetpj - i've seen ur dyno graph with the stock injectors, thats some serious leaned out a/f ratio. Nice site by the way.

So from what you guys are telling me, I can use the stock maf for my 7psi while switching to the SR's 370 injectors and keeping the stock pump.

1)When getting the 370 injectors, you MUST have a AFC to control it, is this correct?

2)Lets say that i get a AFC to tune the fuel, will I still need a boost dependent FPR? I'm thinking no.

3)Is the purpose of the hack maf for engines with boost over 10psi or whatever the stock maf's limit?(tried searching for this answer but everyone keeps talking about JWT or how to program the S-AFC).

[huguetpj]

huguetpj - i've seen ur dyno graph with the stock injectors, thats some serious leaned out a/f ratio.

I know

1. You must have something to control them, be it AFC, Emanage, JWT ECU, standalone, etc.

2. No you don't

3. The main idea of the hacked MAF is to lean out the 370cc injectors by having more unmetered air enter the engine. The side efect is that a bigger MAF has a higher CFM limit. Don't know if the difference is much though.

[racin-type]

Now i'm confused, how come we are trying to lean out fuel by adding more air?? Isn't it the other way around, by measuring air we add the right amount of fuel?

If its a must to use the AFC with bigger injector can't we use the AFC to lower fuel pressure to how much air is coming in?

[huguetpj]

Simple. If you were to just install the 370cc injectors on your car it would drown the engine in fuel. Why? Cause the engine reads X amount of air and injects Y amount of fuel based on it's preprogrammed maps supposing you have 270cc injectors at 43PSI of fuel pressure. If you install 370cc injectors, in essence the ECU would inject 37% more fuel. What the hack MAF does is lower the MAF reading so that the ECU doesn't try and inject as much fuel. The gain here is that bigger injectors won't reach 90% duty cycle as fast and thus the ECU can keep injecting more fuel at higher CFMs, at leats until the MAF readings reach 5V (their max).

The AFC does basically the same. It changes the voltage level of the MAF reading going into the ECU by X%. This percentage can be positive and negative, so, for example, if you were to install 370cc injectors you could start by having the AFC at -35% all around in essence having the 370cc injectors work like 270cc.

Tuning is a bit more complicated but that is the general idea. Hope I didn't confuse you more

[daniel240]

the cheapest fuel setup would be a hacked mafs and 370cc injectors. you can pick up some used 370's for around $100 or less. thats the same cost as an fmu would be only much safer and you would be able to run a little higher psi.

[MikeMurphy]

Heh, your not high. im 180-185-190-185

also, dont forget to retard your timing a bit

There really is no excuse for a walbro and 370cc injectors at least. You can find an adaquete AFC very easily and for fairly cheap.

[racin-type]

retard timings on the list thanks for suggesting.

Its not that i don't want to shell out the money for these parts, if its necessary i will get it. but if it is not a must then there is no reason really, only maybe for a peace of mind.

Now i understand what the AFC does. but do you have to get the upgraded maf for the fuel leaning? can you control the stock maf to lean the fuel?

ps - anyone know whats the MSRP of the RevHard turbo manifold? They didn't have a price on their website.

[huguetpj]

retard timings on the list thanks for suggesting.

Now i understand what the AFC does. but do you have to get the upgraded maf for the fuel leaning? can you control the stock maf to lean the fuel?

You can use the stock MAF, with the AFC.

[C-Kwik]

I paid somewhere between $4-$500 for mine from XS- Engineering. You might be able to find it cheaper than I did, but I needed to find a place that had it in stock. I'd have to find my invoice to verify the price.

[racin-type]

thanks for the price quote from your memory. I was thinking of that manifold because in principle its better than the JGS log mani but with my low boost/economy setup it probably wouldn't make a difference. Just wanted to see how much that difference costs.

I've read that the Z31's had T3s but how about the Z32? Anyone know where else these small turbo's came in factory turbo cars?

So heres the setup running at 7max:JGS log manifoldinternally wastegated T3370 injectorsSAFCBOVsmall intercooler2.5" piping all the way around.

thanks everyone for answering my questions.

[C-Kwik]

Well there are a lot of manifolds out there now. If you are building from scratch, you have a lot of options. I bought mine as a replacement for an existing kit so I needed one that would just simply bolt-up. Even then, if I didn't need it in such a hurry, I would have ordered the one Chris May used in his 240sx as it was a direct replacement for the Rev-hard, but way better. I believe someone has a equal length version out that is a replacement for the Rev-hard as well. These may cost a little more, but should work somewhat better. The Rev-hard requires some prep if you want it to last. The one Chris May used does not. I don't remember much about the equal length one.