Hammerhead

Hi All! I've done quite a bit of research on this, but all the information combined is inconclusive to me. I am asking advice, because my car is a bit of an anomaly, and as such doesn't follow much of the path of development many of the members' cars on this forum have pursued.

OBJECT: To Reduce My Fuel/Air Ratios at Idle, Resolve Some flatspotting (hesitation) around 5000 - 6000 RPM

A Little History: My kit was built by 93mimi, a forum member here in Tampa. He had run the kit for a couple of years on his car @ 16-18 lbs boost with no considerable issues. The kit has been on my car for a year and has been amazing, with the exception of the aforementioned A/F ratios. I have the GReddy TD04 kit, GReddy manifold, RM 2.5' DP, 2.5" custom Flowmaster exhaust with cat, NPR large I/C, GReddy Type S BOV, an original-type Hallman MBC, Vishnu dual-feed fuel rail, 440CC injectors, a newly-installed Walbro 255lph HP fuel pump, RX7 AFM and a new narrow band (stock-type) O2 sensor @ 16lbs boost on 93 octane pump gas.

I have a JR AFPR in a box in the garage. Would I benefit from the addition of an AFPR? How about an MSD timing controller? As I said earlier, I really only want to manage the idle without adversely affecting WOT performance. BTW the car runs like a scalded dog otherwise and I love the simplicity of NOT having the extra piggy backs, etc.

I had thought about leaning it out a tick or two (via the AFM) and advancing the timing slightly.

Any suggestions?

Braineack

iTrader: (62)

Without idling on a dyno with a sniffer a WBo2 of your own, how do you know you are rich/lean at idle?

easiest thing however would be to back the idle mixture screw on the AFM back a complete rotation.

bripab007

The 255lph Walbro pump sounds like once component that could be an issue.
What was it running before that?

Has the car basically had these AFR problems since the day you bought it? I would echo Brain's comment: how do you know it's got bad AFRs, and what are those AFRs?

Hammerhead

IT exhibited these probles before I dropped the Walbro in last night.

As I understand it, an over rich mix will cause the idle to 'hunt' up and down, 'bouncing', if you will - and the car does this. If I lean out the AFM, the 'hunting' stops. Plus, it smokes out the tail pipe and is obviously way rich. My dyno run is posted in the dyno section, but that is now several months old.

Joe Perez

iTrader: (8)

16 PSI, on 440's & a 250HP pump, with no timing control and the stock ECU?

Yowsa!

Seriously, though. You really should put that car on a dyno with a wideband O2 sensor so you can actually see and log what's happening under load. Having the input of a dyno operator experianced at tuning turbocharged engines wouldn't hurt either.

The Walborough 255 HP is a lot of pump. I'm running 440s on the stock, 16 year old fuel pump. At 12PSI of boost I've got more than enough fuel, though admittedly I am using an eManage Ultimate.

I'm assuming you installed this beast to deal with a perceived lean condition under boost? If so, you'd be a lot better off going down to a smaller pump and putting that JR AFPR in.


What is your ignition base timing set at? And don't say 10 BTDC because I will reach through the internet and punch you. If you don't want to go full piggyback, you might consider a Bipes ACU with a MAP sensor to handle your ignition timing needs. I'm guessing that your timing is pretty far retarded at the moment, and that will contribute to a lousy idle. The cost is comperable to the MSD box, and it's a much nicer unit.


I'd really suggest investing in a wideband O2 sensor, though without an eManage it's not going to be used to its full potential. It's nice to be able to log WBO2 on the same chart as RPM and MAP, rather than trying to glance down every few milliseconds to see what the gauge is doing. But with some dyno time and a good operator you can probably do without.

TurboTim

iTrader: (9)

+1

My meaningful advice and suggestion is to use a piggyback. Too bad they "are for sissies" eh...

sorry I don't have any advice on cheap things you can do to fix your problems.

I used (still do) a 255 walboro on my greddy kit w/o issues.

rappadan

iTrader: (2)

+2
I ran 1.2 Bar on a pierburg and 6 deg of timing-non intentionally and got some major blow by goin on,ooh yeah and than theres that comression issue i got now....

boostinsteve

The piggy back is going to be the easiest route to performing what you want to do. Good luck.

Fireindc

iTrader: (13)

Wow, 16 psi. Sounds dangerous, if i were you i would go for a bipes and a WB02.

Good luck!

Hammerhead

LOL...don't be hatin'! But seriously, what makes my car an anomaly is that it has this much power, torque and boost with the stock ECU and stock fuel pump, which defies most of the 'accepted' logic about turbocharging a 1.6L Miata. ALso, this kit has been running on my car for over a year and over two years on the previous car. Previously, it dynoed @ 16lbs @ 238HP/255LB-FT. I dyno'd a few months back, but had a serious drop in boost after hitting 16lbs. Had I been able to keep the boost pressures up, I would have been well into the 200s instead of reading 190.7HP/195LB-FT. Of the dozen boosted Miatas in our group, I still came out on top by 2 HP over an NB with the full FMII @ 12lbs. Granted this was on a DynoDynamics rig, which some had complained reads low. For instance, the aforementioned FMII had dyno'd at over 200HP a few months earlier on a Mustang dyno.

My car runs acceptably, but I am now desiring to do some (more) precise and get better than 17 MPG.

Yeah, that was done and my sheets are in the Dyno section. I had to remedy the boost leak and cracked DP before I could do any REAL tuning.

Yeah..I was on my stock pump (17 years old) as well until Tuesday night.

In a sense...yes. I can tune the fuel up to feed the rail at WOT, but idle suffers. I can tune down, but then I'll get pinging @ WOT.

Don't hit me, but I recall that I did set the timing back to 10 or 11 degrees when I installed the turbo. I can get the MSD for next to nothing, so I figured I might go that route if its worthwile.

I had thought about a wide-band, but wasn't sure that it could benefit me, as the ECU wouldn't know how to read it.

I also replaced my Magnecore wires with the NGK blues to see if there was any difference. I also need to swap coil packs to see what difference it may make. Two of the connectors look like they were arcing. Additionally, I am running the NGK BKR7E-11s with a .39 gap.

bripab007

If it only dyno'd 238hp/255lb-ft at 16 PSI, somethin' ain't right, even on the lowly TD04H-15G.

krayzrac3r

hammerhead... props for pushing it like that and having the *****. I know I wouldnt do it lol. Anyways Brian 238 hp/255lb ft at 16 psi is that at the wheels? If thats at the wheels, then I dont see how that is low. People are putting 240whp on average. Unless you meant crank hp then that statement leaves me blank.

Hammerhead

Yes...those were definitely rear wheel numbers and they don't seem low to me either. However, if there was additional engine management, I COULD see how those numbers could be increased, but by how much - I don't know.

If you look at BRGRacers dyno (granted his setup is different than mine) he is generating 243HP/225LB-FT @ 15 lbs. This car was at 238/255. I'd rather have the extra 30LB-FT of torque to push the car!

bripab007

The TD04H should push close to the same amount of air as the 2560, so yes, it seems like 240rwhp at 16 PSI is low, but perhaps that's due to the less-than-optimal timing and fuel delivery.

Wasn't Phil making ~260rwhp with less boost? Guess I've gotta look through the dyno charts.

Hammerhead

I have the MSD and the JR AFPR to install this weekend. Correct me if I am wrong, but in theory, should this allow me to run at the higher idle AFR mix, but advance the timing at idle and the MSD should retard advance up to 6 degrees at boost?

I already have fuel dump @ 4500 - 5500...does the AFPR adjust for this? Sorry for the newbie-like questions' but adding this shizz is new to me.

greddymx5

iTrader: (1)

How the f#ck did you run 440cc injector?? Of course it wil idle like crap....

Trow in the old injectors or 1.8 (at least it will idle ok then.)
For the boost pressure: 6psi of fp for each psi off boost on top off your basic pressure...so : 45(basic pressure)+10x6 =105 psi of fp (on 10 psi....)
Basic pressure is fp @ 0psi , to achive this remove the hose to the oem regulator.
On 1.8 injectors a little more (around 11 psi)
the oem ecu runs well on 250cc injectors (12psi)
This is save.... with some timing....
Don't go over 120psi of fp (100psi is the max for the fuel line...)

Youll probably wont see 45psi basic pressure due to the 255 walbro.So here is what you should do there:get 2 t fittings to t in into the fuel lines.
1 goes to the supply line. 2 goes from the oem regulator to the afpr
connect a fuel line between these t fittings, cut it in 1/2 and place an adjustable valve in there.
The oem fpr can be adjusted at the valve to 45 psi @ 0 psi off boost.
This way the ecu thinks everything is normal.
Boost pressure must be adjusted on the afpr.

Ps do a compression check b4 changing anything. Don't like the power loss.

Hammerhead

I know, I know!..LOL Adding bigger injectors just makes the idle worse. But, perhaps I should explain the idle problem. It will idle fine for a while and then it'll drop, nearly stall and recover. It will drop again in 20 seconds or so and then it will ilde indefinitely.

The idle is an irritant, but I can live with it. What I want to resolve, hopefully without a piggyback ECU, is the open loop dump @ 4500 - 5500. Is that possible to do with an AFPR and MSD?

bripab007

Doubtful. Without a full ECU, there's no way to pull back the fuel in that region without pulling it back in other areas.

magnamx-5

iTrader: (7)

https://www.miataturbo.net/forums/member.php?u=121 ask the original he is still around how bout that. the first to run 400+cc injectors on a stock ecu.

greddymx5

iTrader: (1)

You can trie to lean it out by lowering the oem fuelpressure (as stated above)
As 440cc is more then double the amount youll need 20-25 psi @ 0psi boost.(loose vavuum connection off the oem regulator.)
With the valve you can change this...Not sure what the reaction will be off the injectors due to the low fp.....


Be sure the afpr picks up the fp when boosting....but you are on your own there....

440cc fows enough to support you hp level @ stock fp (45psi) Limit yourself to this max pressure.... (link ecu does this too)

Please get a wideband for this kind of tuning....