BadSS

I'm trying to dial this TPI car in. What's the concensus for the optimal O2 readings under WOT?

Blade

Between 800-900 mV. Don't rely on the 02 sensor to tune your car though. It's really not accurate

BadSS

Well,, .800 - .900 seems like a wide range. I'll set it using the Vericom - I guess somethings don't change.

Grim Reaper

I have heard that around .900 mV is where the optimum reading should be. But your best indicator is what delivers your best e.t.

F22Raptor

Between 800-900 mV. Don't rely on the 02 sensor to tune your car though. It's really not accurate
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I don't get it! If the O2 sensor is not accurate, why does the computer rely on it then?

BadSS

I hear you F22!!

I think they're accurate enough. All the Air Fuel ratio meters use an O2 sensor. And admittidly the 02 sensor ain't no egt monitor,,, but I think it will do. I'll end up dialing it in at the track and monitor the O2 voltage,, just to see for myself.

F22Raptor

All the Air Fuel ratio meters use an O2 sensor
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That's exactly my point. So why do people keep saying it's not accurate? What else can be used to tune an engine except an inaccurate O2 sensor?

MikeH

iTrader: (10)

The factory sensor is only accurate around the 14.7 fuel ratio (part throttle). The dyno guys use a wide band o2 sensor they are accurate thru out the range.

Go to the prom board ask some questions. The guys on there are really into this stuff.

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Black 90 IROC, L98, A4, 323 gear. SuperRamed 406 in the works!

Grumpy

The oem O2s that gm used in the 3rd gen cars are a switching type. Meaning <,44 leaner the 14.7:1, and >14,7 is richer. Period.
The early cars just use and AVERAGE 14.7 so all they need is a rough idea of where things are and swing rich and lean of that.
I have a WB, and still rely on reading plugs.
The EPA, and CARB after all these years still can't even agree on what an O2 sensor in even reading.
They are also temp., and backpressure sensitive. But, it's like so many ol wifes' tales it's been repeated so many times some how pact doesn't matter any more.
For a fun time get a copy of the archives from GMECM, and DIY_EFI, and read up on the tech end of them.
If you want to build you own WB look at GMECM, under members and projects

doc

For best WOT performance, I tune the AFPR so that I get 850mV to 875mV out of the O2 sensor. I think that this range gives you about 13.2:1 air/fuel ratio, which is optimal for power.

The stock or other one wire O2 sensors are accurate enough for the range that you are interested in.


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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(48psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
ET 13.39sec @ 107.21mph
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter.
313.7Hp & 320.6ft-lbf, ET 13.55sec @ 105.1mph
next mod: 4.10 rear gears

Grumpy

If you care to read up on the subject, you'd see the errors in what your saying. If you doubt that they are anything better then switches try the DIY_EFI archives, and the Patent office.
Just read thru the GN site and how popular it is to tune to the O2 and read about all the headgasket problems.
I've actually datalogged the two side by side and you can see the oem swing from 11.8 to 11.2 at a constant .78v..
That ain't close enough for me. Over a .5 difference *can* be a serious problem.
Grumpy
http://www.gnttype.org/carofthemonth...omdetails.html

Kevin91Z

iTrader: (1)

So what are we trying to accomplish here? My PROM is set for 12.3:1 air/fuel, and I get O2 readings in the high 800's. However, I had my car on a dyno with a wideband O2 sensor, and it said I was running very lean, in the high 13's or low 14's. To richen it up do I need to add fuel so I get my O2's in the 900 range?

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

Grumpy

You have to find out what the engine wants, what the AFR says is meaningless unless you know what it wants. You have to measure it's performance and do back to back testing. Takes numerous runs to dial a car in.
There is no way to avoid reading the plugs, and measuring performance.
A dyno doesn't present the same load as running on a 1/4 mile, ignoring the air resistance is like ignoring tire pressure. Even with all the millions of dollars Winston cup car guys spend in the dyno cells they still leave the final timing and jetting for at the track.
Grumpy http://www.gnttype.org/carofthemonth...omdetails.html

Kevin91Z

iTrader: (1)

I have several Diacom runs at the track over the past year. I didnt know the car was lean until I had it on the wideband O2 sensor. The plugs looked ok, but had the orangish stuff from the octane boost on them.

doc

Grumpy,

I respect your comments very much. You have done alot of work on proms and engine data analysis. I recognize that the one wire OE O2 sensors are not very accurate. I take the O2 output readings as a relative number.

With my latest engine rebiuld (AFR 190 heads,
TPIS ZZ9 cam and 2200rpm stall TC), the engine needed more fuel. I went from 48 to 57/58psi on fuel pressure. Each time that I increased the fuel pressure by 3psi, the car got faster and the O2 readings went from 750mV (@ 48psi) to 850mV (@ 57psi). I'm using an XP240 scanner for this. My car will now turn 13.3s at the dragstrip, but I think that the car should be in the 12s.

The AFPR is maxed out now at 57/58 psi. I believe that I still need more fuel, therefore a new prom is required.

I intend to buy the prom burning eqiupment as proposed on this board. I could definitely use your help on this matter.

Can you help me get my car into the 12s in 2001??????????

I'm certainly willing to drive down to Dayton to meet you.




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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(48psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
ET 13.39sec @ 107.21mph
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter.
313.7Hp & 320.6ft-lbf, ET 13.55sec @ 105.1mph
next mod: 4.10 rear gears

Grumpy

87Z-ya

iTrader: (1)

Doc, my car is similar to yours. I have a lean problem and I am running 62psi. I havent decided which way I am going to go as far the computer. Either a speedpro setup or the new accel 7.0. You havent mentioned if your running a good fuel pump or not? I found out it makes a big difference at that high of a fuel pressure. My car was running high 13's and would loose fuel pressure. The original in tank pump had the top come apart and the brushes were barely contacting. Now with my holley forced induction pump I can run the high pressure as a bandaid(the injectors dont like it though). The car went a 12.6@116 last friday with a 2.3 60ft.(hard radials). I was happy for a stock chip. Cant wait to get it really tuned.

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87z 383,afr 190's, crane hyd roller(224/230-.509/.528,112 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, strange 12 bolt, tremec 5spd, , 1,3/4" slp headers.

JakeJr

Most guys agree that at some point increasing fuel pressure runs smack-dab into the law of deminishing returns. You can only increase pressure to a certain point and continue to see positive results.

Once you've gone as high as 60+ psi of fuel pressure you're well past that point. Now your attention has to be directed elsewhere to richen the mixture.

Assuming the PROM is properly calibrated, there are basically two schools of thought on this: Keep the same injectors and increase the fuel pressure or swap to higher flowing injectors and lower the pressure.

TPIS likes the former, claiming better spray patterns with the higher pressure; others take the opposite position. Once you're at 62 psi and are still running lean, then the higher pressure option seems not to be the answer.

Three areas come immediately to mind. Fuel pump/line diameters/restrictions, fuel pump flow capabilities and injector sizing. Unless you're force-feeding the engine, stock line sizes should suffice. Now we're down to the pump's capabilities and the flow rate of the injectors.

I'd opt for the latter and go with higher flowing injectors and, as a result, not have to work the pump to it's max capability.
This plan would also keep the injectors working within the max recommended 80% duty cycle.

Just my thoughts. I'm sure there are others.

Jake



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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

doc

87z,
12.6 sec sounds great. With a 383 and better tuning, you should see low 12s if not high 11. Real drag radial will help also. I'm going to buy the Mickey Thompson ET Streets for next year.

Jake,
I'm still using the stock fuel pump. I notice 2 years ago when the fuel injector is open for 13 msec or more, the fuel pressure would fall off. At 13 msec and above 4500rpm, the fuel injector duty cycle is 100%, in other words the fuel injectors were open all the time. The fuel pump could not keep up. I sent my custom chip back to Car-Pro and had them reduce the fuel curve. That was with the TF heads and reground LT1 cam.

Now with the AFR heads and ZZ9 cam, I need 5 to 10% more fuel. I can't get it from more fuel pressure, so I was thinking that the chip needs to be modified for more fuel. But now I'm thinking that this will put me back into the 100% duty cycle problem. The Car-Pro chip is giving me 12+ msec pulse widths.

My new option is to install new fuel injectors, GM 24 lb/hr injectors, GN 30 lb/hr injectors, or SVO 24 lb/hr injectors (which I have new in a box at home). The problem with the SVO injectors (besides being Ford) is that they are reated at 37psi, which means that if rated at 43psi like the GM injectors, the SVO 24s are really 26 lb/hr injectors.
Not many people realize this fact! I'm going to back off on the fuel pressure alot if I use my SVO injectors.

Will LT1 injectors fit our TPI setups?????

LT1 injectors flow 24lb/hr at 43psi. These might be better for my specific situation.

What do you guys think????

BTW, I just received an 1LE brake upgrade kit from Strainless Steel Brakes. I should be able to stall the TC out at a higher speed now without creeping forward at the start line.

Kevin91Z

iTrader: (1)

Yes LT1 injectors will fit TPI intakes. Just remember 92-93 LT1's use 22lbs, and 94-97 LT1's use 24lbs.

doc

Thanks, Kevin, I did not know that.

Grumpy

A fuel pump will just generate so much work, as you crank the pressure up your volume drops. You can go right past the max fuel delivery and not know it, at 62 PSI, you've got a problem, IMO. I run 62 at 20 PSI of boost, but the system is specificially designed to handle that, ie none of it's oem.

87Z-ya

iTrader: (1)

Believe me I know this isnt the right way to do it. Its just untill I have the time to make it right. The 255lph forced ind. pump from holley I got is a good piece. During my pass at the track I recorded with a camcorder at my fp gauge and at 6300 rpm's There was no loss in pressure( I know its irrelevant to volume). But like I said its a bandaid.

JakeJr

Just as a point of reference, with my 415 at WOT, PE mode, the max pulse width Diacom records is 8.5 ms and that's with TPIS 27 lb injectors; 44/52 psi fuel pressure.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9