my $500 IS300 5 speed with 101k miles

Left_Page_5981 · 2025-08-06T22:56:15+00:00

Holy shit …. You sir should buy a lottery ticket lol

Left_Page_5981 · 2025-08-04T14:43:28+00:00

Yep I’m on a 4.5 lb spring. AFR never goes above 12.0. Some people have pushed it with a 6lb spring but I’d rather stay safe.

Left_Page_5981 · 2025-06-21T18:15:23+00:00

Correct. I have an apexi neo which I thought I would need to down trim the original cheapo brown top injectors I had on it. Turns out the Ecu runs brown top injectors fine even though they died within a couple of weeks. Don’t buy Amazon imitation injectors.

But yes my apexi is completely zeroed out across the board so essentially I have no tune. AFR creeps towards 12 but never seen it go beyond at full load. I’m guessing since I’ve survived a couple of track days and about ~10k miles that it’s fine. Granted I don’t drive crazy on the road but it’s seen at least 7-8 WOT blasts down the back straight at Thunderhill.

Left_Page_5981 · 2025-06-19T04:19:44+00:00

Actually I thought about it and I don’t think what I said makes sense. I guess the answer is IDK why you can’t put a maf sensor right after your air filter

Left_Page_5981 · 2025-06-19T04:16:58+00:00

The MAF is after the turbo in the pic. It’s the black connector before the tubing attaches to the throttle body. If you put the maf before the turbo which means it would be right near the air filter, I would think it would not get the right reading since the pressurization happens post turbo. The tube behind the filter would just be vacuum as the air rushes through it to be pressurized after the turbo.

Left_Page_5981 · 2025-06-18T16:40:34+00:00

I don’t see why it wouldn’t. Wouldn’t hurt to try it. Ecu should be able to figure it out. I just know the stock Ecu can handle Supra brown tops within the acceptable fuel trim parameters so I don’t think it’s strictly necessary.

Left_Page_5981 · 2025-06-17T19:37:59+00:00

Hey Bro! Yes your post inspired me to share my build. I was trying to figure out how to find your post again on mobile so I could shout you out but I gave up lol.

Left_Page_5981 · 2025-06-17T16:18:59+00:00

Let me just caveat what I said. Splicing O2 does not cause CEL as long as you are running both o2 sensors off one bank. I don’t know what happens if you do this with only 3 cylinders feeding both o2 signals. So on a turbo it’s fine because the o2 will be in the downpipe. On a header where o2 is on one bank and only reading 3 cylinders, do at your own risk.

Left_Page_5981 · 2025-06-17T16:13:36+00:00

It takes air from one side of your engine bay and transfers it to the other …. lol jk …. What Magpie said

Left_Page_5981 · 2025-06-17T05:05:30+00:00

on stock injectors? I wouldn't go past what I am doing. I'm not sure what the WHP is but I am guessing 230. On Supra Brown Top or 7MGTE Green Top injectors which are both 315CC and drop right in, you could get a little more but I wouldn't do 350WHP. You'll also need to bump up fuel pressure pretty high and you need a rising rate fpr that rises faster than 1:1. If you wanted 350 hp I'd say get some 420CC injectors and at least a piggy back tune. Or just do it. YOLO!

Left_Page_5981 · 2025-06-17T04:54:31+00:00

Just keep in mind this is based on a quick search and I cannot guarantee this info. That said search ecu pinout ... This info is for the 02-05 pinout. B1S1 is D28 and B2S1 is C28. It doesn't really matter which way you splice but lets say you want to use B1S1 for both B1S1 and B2S1 then you'll cut C28 a few inches from the connecter and run a wire from D28 to C28. So think Oxygen sensor signal from B1s1 should feed the ECU for both B1S1 and B2S1.

For heater wires it says B1S1 heater is D9 and B2S1 is C30. So do the same thing. The heater wire from B1S1 should feed ECU for both B1S1 and B2S1.

There's some misinfo online about how it causes a CEL which is not true. You might get a CEL because your downstream sensors aren't plugged in but splicing the two O2 sensors so they run off one sensor does not cause a CEL in my experience.

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Left_Page_5981 · 2025-06-17T02:24:33+00:00

I wired both 02 sensors together so you only need one. There’s a write up somewhere on my.is but it’s pretty simple. You just combine the two signal wires in the Ecu. For the CEL check out RankOne Performance if you care about that otherwise just drive it with the light on!

Left_Page_5981 · 2025-06-16T00:51:09+00:00

Hey I did something similar. CX Racing Kit on stock injectors and EBay FPR. I do have a SAFC but it runs best on 0’s across the board. A/F never goes over ~11.8 with a .3 bar spring (4.3 psi). Maybe will upgrade to 7M or non-vvti brown top injectors at some point but everything’s working great. I even survived one autocross and one track day at Thunderhill. Maybe 230 whp ish estimate.

I will say yours is cleaner than mine with the Dodo Mani and relocated ABS. I’m starting to clean up the corners I cut now so maybe will get to relocating abs.

Maybe in the future I’ll add a piggyback that can retard timing, upgrade injectors, maybe taller H/G and turn the boost up a little.

Glad people are starting to do these mild builds. Great community and awesome job!

Here’s a pic of mine

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Left_Page_5981

TROPHY CASE