seank

I think I might not have my boost controller setup right but I have another concern. My waste gas has a 10 psi spring, but it sure sounds like it wants to build more boost. Can you tell by looking at this log file if my turbo has "run out of steam".



Im running a 355cid LT1, T70 .96exh, stock manifolds, 2.25" crossover, 3.5" turbo back exhaust, PowerEFI megasquirt ecu

Thanks,
Sean

Old Geezer

iTrader: (3)

Looks like it's lean, @ 13.7:1. 3*KN, at 10psi, at 77% DC..Inj Dc looks to be unstable.
What is the back pressure ratio w/ stock exh manifolds?
FP boost referenced? What is it @ 10psi boost? Base setting?
Closed loop correction enabled?

seank

I'll have to put a gauge on the exhaust and check the ratio I hear 2-3 is acceptable. All injection regulators are boost referenced. at 10 psi it is making 10 psi more fuel pressure. Are you saying that it wont make boost if it's lean? AFR is pretty stable(a bit lean as you noted) so I could care less what the DC is as long as its not maxed. It is in closed loop with 15% authority. I'll adjust the ve tables against the log and get the afr closer to the target (12.5).

Old Geezer

iTrader: (3)

1.Exh backpressure should not exceed 2x the boost. [Checked immediately below the turbo.]
2. Not all FPR's are boost referenced.Depends on the system.
3. 12.5 AFR is a good N/A A/F ratio. If u r going to spend the time on the maps, I'd suggest making the changes to cover the intended rise in boost target.
4. Lean is mean, but too lean and you know what happens.
5. Where do you have the O2 sensor installed?
6. What do the plugs look like?
7. @ 77% DC, and "only" 10# boost, you are fast approaching the safe limit of 85%.
A 76 should help the max boost thing.

seank

1. I'll have to check where the stock o2 bung is in the manifold(6" before the turbo). There is no other room to add a bung

2. Curious, can you give a specific example of a FP regulator designed to work with FI that isn't boost referenced? By the nature of the design any regulator that adjust for manifold pressure(vacuum) should adjust for "boost"

3. Going from 8 PSI to 20 I have it set to transition(AFR target table) from 12.5 to 11.5 AFR. I'll have to run the ve table against the wideband o2 logs, as you can see its lean.


4. Yes I do, I killed my 496 boat motor like that

5. I have the o2 2" after the turbo

6. The plugs look ok actually..... I don't stay on the throttle more than 4-5 sec at a time because my tune up is rough

7. Judging by my DC/PSI, it sounds like I don't have too much back pressure. I have 48#/hr injectors I really would have thought the 70mm would have been good for 600 RWHP(12-14# boost) of course those are my rough estimates.

Old Geezer

iTrader: (3)

1. Having the O2 that close to the turbo is going to subject it to excessively high heat, and pressure.[Skewed readings, shortened life.] I'd suggest it be in the DP, and at least a foot away from the turbo outlet.
2. FPR setups on stock F bodies w/ blowers are not boost referenced. Guys get them to work within reasonable boost limits. Correct: Most any FPR designed for reference can be used to control fueling on FI applications.
3. DC/psi vs backpressure?? I don't understand that comparo.

My calcs show that a "guesstimated" FWHP of 675 is what you have to fuel, if you want 600RW. Using those values, I see the need for an inj that'll flow 59.5#/hr.
If your 48's are 48 @ 3 bars, you are outta inj. At 58psi, the flow is 55.4#/hr. All calcs done at .85DC.

Zombie

iTrader: (2)

If that a/f is accurate it's much too lean and costing you power as well as risking the engine. It's best to target mid 12's for spoolup and then richen it up to 11.0-11.5, I personally tune 12.5 to 5psi, 11.5 to 8 psi and then 11.0 over that.

If your knock is real it's most likey because it's lean, i'd fix that ASAP. Are you using the MS for boost control? You have a very odd dip in your boost. You will just about run out of injector as soon as you set your fuel richer. I'm running 95lb/hr injectors on my MSII without a boost reference FPR (70psi at idle) and they run and drive great. I would reccomend them if you have a MSII or a MS with the flyback setup.

Your turbo should be good for around 15psi on that size engine.

2002ws-6

iTrader: (5)

Zombie that first paragraph was exactly the info I've been looking for. How do you recommend the timing curve. Should it Run like its N/A till a pound or so of boost and the pull more with RPM and boost? Sorry to hijack, but I have the same turbo, and similar other parts just mines out back and an LS1.

Zombie

iTrader: (2)

I run n/a timing until 100kpa then slowly start pulling timing. If i run 30 at peak tq n/a I will usually start pulling 1 degree per psi. This varies with the compression and octane of gas the car is running so take that with a grain of salt. I also try to get max timing by 2500 rpms, pull 2-3 for peak torque, then add 2-3 back in by redline.

seank

My mistake, I meant to say I'll put the pressure gauge where the stock o2 sensor goes. My wb (http://www.14point7.com/JAW/JAW.htm) 02 is about 2" after the turbo in the DP

Let me clarify my thoughts about the dc/psi comparison. If there were excessive back pressure in the exhaust then the engine would be "choked" and that high of a DC at a certain PSI would make it really rich since the engine is not "breathing" see what I'm saying now. Thats why I was guessing that my back pressure was in the realm of normal for my application.

I calcd about 700max FWHP and thats why I went with the t70, I figured it would be a good match for everything else.

seank

EGT is VERY useful in determining the best timing values.

seank

Yes I'm using ms for boost control. Thanks for the AFR targets, I'll follow your advice and see how she runs. I'm using the PowerEFI PNP(http://powerefi.com/shop/index.php?m...c7d3391846e48f) setup which utilizes the V3 board that has the fly back circuits. Who makes your 95# injectors?

Zombie

iTrader: (2)

Details on using an EGT?

I've got access to a Mustang dyno so I just set my values based off the real time HP reading when tuning. Hold the car at a load point in a cell and adjust it up or down and watch for what gives best HP.

seank

That's actually a better method IMO to get max HP. I would have to say though that using EGT readings are a close second assuming you're using the right octane fuel for your combination(not too high and not too low). When you increase timing the EGT should fall meaning that more of the thermal energy is being harnessed into mechanical energy. When you have too much timing and approach spark knock the EGT reading will go up. Here is a problem I have run into, if you have too much octane(say 110oct fuel for a 8.8:1 #15boost) for your combination the EGT reading will keep going down even after you have reached optimum HP timing. I have seen a 30-40 HP loss before an engine starting to knock, due to too much advance. On the flip side too little timing will generate high EGTs wasting power that otherwise would have been harnessed as well as putting your exhaust valves at risk.

Hope that clears it up a bit for ya.

Zombie

iTrader: (2)

I've used EGT's to tune off in the past, but have always found them too slow and inconsistant to be useful except for an "oh **** i'm melting the pistons" gage.

I've lost power from over timing cars too. I personally don't run higher than 100 oct in my car. I run 91 oct to 13psi for street and 100 octane to 20psi for racing. With the ST80 it seems I can run more timing and 15-16psi on 91 octane vs what I could on the 76, i'm guessing because of lower back pressure and better efficiency. I don't chance it though, 13psi is plenty fast on 91 octane.

To the OP, check your back pressure before the turbo, if you have a restrictive muffler in your setup it will limit you on boost (I had this issue with a 14psi spring only showing 10psi until I changed the exhaust after turbo, then it went to 14psi).

seank

I would be happy with 13-16#, and yes your exactly right you can run more boost with a more efficient setup(bigger turbo) on the same fuel. I would be interested in taking a look at your setup, I'll be in vegas this fri/sat I need to drive my friend to an eye surgeon.

seank

That seemed to do the trick, now for bigger injectors.

Zombie

iTrader: (2)

Awesome, glad to see you figured it out, 19psi now huh? Time for bigger injectors, your a/f is still quite lean. Target 11.0-11.5 to add some safety to it.