View Full Version : SR20det Lean at WOT

03-08-2020, 09:17 PM
Just got done with engine rebuild. Engine runs good accept at WOT it gets lean. Starts out at 11-ish at low RPms and climbs to 15-ish by 3 to 4k. Here is a Datascan of the data. Any ideas?


What we have:
• S13 SR20det Redtop with stock internals
• G28 Turbo
• Wablro 255 high pressure with dedicated 12 gage wires from battery
• MAF from Ebay (Chinese—checked for coronavirus)
• AEM AFR wide band O2
• EGR delete
• Charcoal canister delete (vent to atmosphere)
• No BOV (plan on adding after its running)
• Z32 370 CC injectors (purple and new)
• Z32 fuel filter
• ISR adjustable FPR
• Stock 62 ECU (opened up and confirmed stock)
• Wiring Specialties wiring harness
• Datascan
Electric fans (coming on at 160 deg F--need to adjust)
What we know:
• Timing verified at 15 BTDC (light and Datascan)
• Double checked CAS and mechanical timing
• Boost leak checked (20 psi)
• Compression: good
• Test TPS with Datascan (car off): 0.45 and 4.1 volts
• Vacuum leak: checked (with smoke)
• Fuel pressure jacked up to 70 psi, still leans out
• Checked exhaust leaks
• At Idle:
o Fuel pressure around 41 psi (set to 44 with engine off)
o RPMs: 900
o Vacuum: -20 Hg vacuum
o AAC at 10% when warm
o AFR around 14 to 15
o Alternator Volt: 14 (measured at alternator and battery)
o ECU voltage around 13.0 volts
o TPS showing closed on DataScan/Consult.

03-08-2020, 09:26 PM
How much psi

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03-08-2020, 09:35 PM
We haven't had it above 4k, so max boost we have seen is 2 to 3 psi. planning for 7 to 9 psi.

03-08-2020, 09:37 PM
Can you check fuel pressure gauge while loading it up to make sure it is holding pressure and also rising with the boost , if it is then it’s most likely injectors or tune . If it isn’t then it’s fuel system , faulty fpr or fuel pump

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03-08-2020, 09:58 PM
Ok thanks, we cranked the fuel pressure up to 60 psi and ran it to try to force it to go rich. When we did that we didnt see the fuel pressure rise with boost--stayed about the same... shortly there after we burned up the fuel pump, which ended that game. I assumed it that it wasnt a valid test because the fuel pressure was so high. I will do a re-run of that test with fuel pressure set normal. Since we got second fuel pump in now with same symptoms, so not likely fuel pump. FPR could be problem. At idle we only getting drop from 44 to 41, when it should be down to 36-ish. We have dedicated line from the throttle body to FPR --which we have changed out and zipped tied down.

03-09-2020, 07:32 PM
We did a run with a GoPro watching Fuel pressure--it rises nicely with boost. We are getting an Apexi and Z32 MAFs. These are two upgrades we were planning to do anyway. If they dont work we are left with injectors. I am concerned that the AAC is sticking on when we go WOT. If you see in the graph above. AAC is at 8% when idle and climbs to like 20% when at RPMs. Also our TPS voltage at WOT is only slightly over 4.0 volts.

03-09-2020, 08:24 PM
I was going to suggest fuel pump wiring until you mentioned the GoPro detail. By now it's more than normal for oem 30 year old S13 wiring to fail to supply ~13v to the fuel pump making it fail to keep the needed pressure under load. It's easy to miss undetectable when setting base fuel pressure at idle because under load is when it fails to keep the needed pressure.

I feel that shit like this is why sometimes the haggard cars (i.e. diy sketchy but newer/thicker fuel pump wiring) are sometimes more reliable than the ones we try and keep original.

...But you already checked that.

03-10-2020, 06:38 AM
The stock injectors and stock computer are just barely enough for a stock turbo

if you put anything besides an original t-25 on it, it will run lean and damage the engine
The programming for the factory turbo is actually kind of lean compared to how we usually tune these, but it works fine because of the extraordinarily low flow rate of a stock turbocharger (barely 200hp from most used T-25 units will hardly harm an 2.0L with a slightly lean a/f ratio say high 12's to mid 13's)

You need an apexi Power FC L-jetro, some 740cc injectors, a real quality turbo capable of 44lb/min minimum, and the Z32 maf all working together in front of a 320lph fuel pump like the aeromotive stealth, to support any reasonable measure of power when compared to todays standard expectations for gasoline engines.
The sr20 also need a camshaft upgrade to get from 320rwhp mark to the 350-400 ranges with reasonable boost pressure.

03-10-2020, 08:25 AM
Oh stock ecu ? Just get nistune, z32 maf and 740 cc injectors and you’ll be good to go [emoji108] no need for costly aftermarket ecu

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03-10-2020, 11:44 AM
Stock ecu--rip

Need a standalone unit..z32 maf, good fuel pump n run new fuelpump relay.

03-10-2020, 05:40 PM
Oh stock ecu ? Just get nistune, z32 maf and 740 cc injectors and you’ll be good to go [emoji108] no need for costly aftermarket ecu

IMO nistune counts as aftermarket ecu.

03-10-2020, 09:56 PM
370s should be safe till about 260 whp. Shouldn't lean out under 10psi on a t25 or s14 t28.

03-12-2020, 12:21 PM
I'm gonna agree that it's the injector/ecu combo.

Going through a headache of my own after throwing 600cc injectors z32 maf and nistune board at my t25 redtop, fpr confirmed to be bad after install and is choking motor with fuel in boost. FPR would usually cause an overfueling issue if im not mistaken, underfueling has got to be related to the smaller injector size and/or ecu not bening able to handle data parameters you're throwing at it

03-12-2020, 02:44 PM
Dont care what other setups have worked...

With a proper cuel setup, maf and ecu....if the motors asking for more fuel(lean) then give it. Needs bigger injectors so be it...

03-12-2020, 09:01 PM
OK, thanks for the advice. I'll let you all know what progress we make w ECU, MAF and injectors.

04-12-2020, 08:53 PM
Wanted to give an update. Car is running pretty good. We made three major changes all at once...we got a Apexi PFC, a Z32 MAF and beefed up the battery ground cable (went from 4 gauge to 0/1 gauge). I can't say what fixed it, since we did all at once, but I think the battery ground was key. Voltage went from 13 to 14, so I think that was critical. Now we are trying to learn Apexi Power FC.

04-17-2020, 02:54 PM
now it needs some 800cc injectors, and a cam upgrade if you haven't,

and a top mount turbo capable of flowing around 50lb/min

Then the Z32 + PFC will be a worthy additional

04-19-2020, 10:52 PM
now it needs some 800cc injectors, and a cam upgrade if you haven't,

and a top mount turbo capable of flowing around 50lb/min

Then the Z32 + PFC will be a worthy additional

KingtalOn, any preference on which injectors?

We got some BC0205 cams waiting to go in.

Also I read a some previous post you made. You made reference to "your map" and an Excel file. Is this anything that would be helpful to me?


04-20-2020, 04:21 AM
Side feed HKS or similar is ideal because drop in oem style is simple and effective.
800cc is a very tiny injector. It doesn't need a complicated fuel system.

Honestly if you didn't mind the extra cost of E85 etc... I would even suggest haltech + flex fuel would be a hit, go farther.
Use a 1200-1500cc injector though. Now you can upgrade the lines and pumps and make it worth the E85 flex.
That is the first piece of the ultimate street setup.
So, if Alcohol content auto-adjust = step 1.
then step 2 is aux systems i.e. methanol, nitrous mostly. Slap on another 200hp or so progressively to whatever you've got and it's all ice cold ingredients with octane improvers.
Step 3 is traction control algorithms, wheel speed sensors, microprocessor finite control of wheel speed and direction. Which you'll need now cause of the nitrous lol
Step 4 is vehicle center of gravity control and suspension integration, magnetic and electrical control systems which correct vehicle speed and direction using vector state space approach, to keep you from flying off bridges at 180mph after starting from zero some six or seven seconds ago
Step 5 is a flying car (whether you like it or not)

Notice how the gateway drug is always nitrous

There might be an excel file floating around to help with tuning a power FC base map.
Actually just today I was looking for a place to upload my power fc related files from 2002-2008 I have stocked up. Zilvia doesn't have a place for them.

fwiw heres a 800cc injector sr20 w/ top mount 55lb/min turbo, V-band style (tiny) exhaust, ~28psi of boost, 93 + traditional meth/water 50/50
And of course PFC + Z32 for tuning on a commander only (no laptop necessary with L-J PFC)