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Discussion Starter #1
Guys,

I installed the VFII supercharger and drove it spiritedly for 3 weeks (only 1 autoX day) till the motor one night decided to lose all power, blow oil and smoke out intake filter, and seize up. My friend and I disassembled the motor and found 3 pistons had seized rings and broken ring lands from detonation (see Picasa album below). All 3 cylinder walls were also obviously damaged.

A new Toyota short block from MWR and BOE surge tank were installed and set to 47psi at idle. A Larini de-cat pipe was heat wrapped and installed during the rebuild which Jermaine mentioned would not cause any additional problems. The dyno session today confirmed that the motor was still running extremely lean (>15:1 @ 7k rpm) :wallbang:. Any ideas would be greatly appreciated.

https://picasaweb.google.com/107666765286885491188/LotusBlownEngine#5755918049494121186

https://picasaweb.google.com/107666765286885491188/LotusBlownEngine
 

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Carbon Fiber
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I'd check fuel pressure, I heard if u have the gasket wrong on the fuel pimp lean conditions can happen. I too have the vfII kit and beat on it nice n good with no issues.
 

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I can't believe it runs at all with the uber lean A/F and forgive me but it is incredibly stupid to do a power run at all with A/F numbers like that. Hopefully one pull did not hurt it.

One simple word. FUEL. You lack one or more of:

1. Adequate fuel pressure at higher injector duty cycles
2. Adequate injector capacity or clogged injectors.
3. Proper mapping in the ECU

You might have a really weird issue with the fuel rail, but 1-3 are good for starters. For example, the idiotic stock Elise fuel system has no in line fuel filter, just a sock on the pump and it is not impossible for debris to get to the injectors.

Your idle fuel pressure means very little. I'd probably clean and test the injectors and monitor fuel pressure under boost.

But above all else, ABORT all power runs unless and until you are 100% sure you get A/F below 12:1

Upon further reflection, the A/F was incredibly lean, even more so at low rpm so I would worry about a fundamental injector to map mismatch (injectors way too small) or bad gas that clogged the injectors.
 

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Plug Whisperer
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It's fair to rule out a fuel supply issue... She was lean on the stock system and the surge tank is a new addition and is good for well over 400whp... so you're OK there...

Sounds like a mapping, electrical, and/or injector problem...

Hope you find it before this motor goes... Get a WB 02 for safety...

Phil
 

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Plug Whisperer
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To expand on Keith's bad gas clogging injectors, Sunoco high ethanol race fuels turn to black gel if left in the sun...

I doubt you're running a race fuel like that, but something to be aware of...
 

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Discussion Starter #6
Thanks all. I did find a torn rubber seal at the outlet of the in-tank Walbro pump when the supercharger was first installed. I replaced the seal, trimmed the pump assembly a little more, then checked the seal days later to make sure it was still intact. This was all before the engine went kaput.

If I had known the AFR was that lean I wouldn't have made the AFR dyno run in the first place today but I guess that was the point. This is also why we stopped at 7k instead of up to the limiter.

The supplied RC 550 injectors seem standard for the VFII kit. I made sure to keep the plastic caps on before installing those to keep from debris entering. Never used race gas. Only 93 octane at the pump.

The very lean condition at low rpm makes me veer towards the tune. I remember fuel trims at idle were less than +5% before engine blew. Acceleration seems smooth at ~50% throttle but does not feel smooth at slight throttle inputs. Feels as if someone is tugging backwards on the car at partial throttle.
 

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Yea I think you can rule out fuel pump, although as kverges said you really want to check pressure at WOT not at idle to be 100% sure.

Also check the MAF and clean it.

You will likely want to invest in a wideband o2 at this point so you can keep and eye on things. Also a log of some critical engine parameters would likely help a TON in diagnosis. Should point you in the right direction.
 

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Plug Whisperer
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FWIW- You can use 1/8NPT fitting to route your fuel pressure gauge to a place you can see it for testing purposes.

The only reason you'd be shy on FP with our surge tank is if there's a wiring problem, but it would be more probable that it will either work or not work... not something in between...

You an data log your car's running parameters with an Innovate LM-2. Just keep the number of items to log down to 4 or less or you'll overload the data stream. it comes with a WB02 as well so you could log that as well and send the data to me for a peak...

-PV
 

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shay2nak
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it's lean everywhere so i don't think it's the tune. Is the tune for the decat you have? I don't think the decat will lean it out that much. Honestly i've never seen a car run that lean.
 

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it's lean everywhere so i don't think it's the tune. Is the tune for the decat you have? I don't think the decat will lean it out that much.
...
For the record - I think it is the tune. Was the tune for a cat or no cat?
The shop doing the tune would have been the shop doing the dyno run???

One way to find out is to put the old cat in it.

If removing the cat makes 20% more power, then you assume that it is not from more fuel alone.


...
Honestly i've never seen a car run that lean.
Never "run a car that lean", or never seen a "car run that lean"?
They run them leaner than that, but usually not under heavy loading.
 

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The wrong map can cause it to be lean everywhere. For the record - I think it is the tune

How much horsepower is this VFII supercharger supposed to put out?
 

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re: Bad AFR

It looks like you well on your way to destroy a second motor...

Detonation can destroy a well built engine in one combustion cycle. Stock Elise motors are not that well built for boost :)

Runnig it up to 7k on above 15AFR is pretty foolish (I am using a very polite word, here).

On the other hand, it should have grenaded, if it truly was at 15AFR and full load on boost to 7K. Is your AFR sensor working? Did you pull the plugs and check? Did you hear anything? did the exhaust 'pop'?

I would always recommend the following when installing aftermarket super-chargers:

1. Install FP gauge where you can see it.
2. Install AFR gauge where you can see it.
3. Make sure the set-up has a knock sensor. This provides limited protection. As the detonation will happen before knock sensor hears it and ECU reacts. It provides damage control.
4. Run the car idle to 2500RPM at full throttle observe FP and AFR. If all is OK
proceed in 1000 RPM increments.

You should pick a supplier that can provide you with a good tune and used his engine for testing :) I have seen many people that 'knew what they are doing' blow up engines while tuning on dyno. There is lots of video evidense on youtube!

I have built and tuned a number of engines. I always get a proven starting tune from someone. Then I back off the timing and increase the fuel. I follow the procedure above to trim the fuel down and adjust the timing. Extra fuel is always safe! If I cannot get a rich condition to start, I start looking for problems.

Anton
 

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Discussion Starter #14
Jermaine just told me in a PM this morning that the fuel pressure should have been set to 58-60psi. I've always read 47psi for most, if not all, other setups hence why I set it that way. This makes sense why it is lean across the board.

Ordered an AEM wideband shipped overnight last night. Phil, didn't see your msg about the Innovate gauge until this morning. I will make an 1/8" NPT extension to be able to read the pressure @ WOT under load.

Smoke poured out around the MAF when the engine died. During the rebuild, I checked the MAF o-ring and it was far too large which explained why it wasn't sealing. Previous owner replaced airbox w/ the TRD/cup box. The o-ring was replaced and it now properly seals. MAF was also cleaned with MAF cleaner.

Yes, the VF2 still uses the pre- and post- narrowband O2 sensors. Jermaine said that the decat shouldn't cause any problems even though the tune was for a cat and I agree it shouldn't change too much, especially this much. My problem is probably the fuel pressure setpoint mentioned above. The tune was a standard VF2 reflash from Vision Function (no custom tune).

I was expecting 280-290hp but measured 220 and 240 on 2 runs on the local dynojet (@ Dynolab) before engine went out. "Before" measurement was 165-169whp (NA) which was on spot.
 

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Makes sense, that is a lot of HP to be making with injectors which are only RC550's. I was wondering how they were getting away with sizing them so small. I am around 265 HP (crank) and (I believe) my injectors are a higher volume part.
 

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Plug Whisperer
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I'll give Jermaine the benefit of the doubt and assume he hadn't had his coffee yet, but that fuel pressure info is bogus.

Stock fuel pressure is ~47 psi and it's essentially static. That said, it 'decreases' as demand for fuel goes up because of a combination of the undersized fuel pump and restrictive pump mount- but it's suposed to be static:rolleyes:

A 255lph pump will typically bring the FP up to about 50psi at idle, but again through the stock system it will decline from there- albeit at a lesser rate than the stock pump would. I have the flow data and actual logs of this on my website from the tests we did back in 2006 or 7...

With our surge tank, if you set it at 47 or 50 psi it will stay there at your power levels +/- 0.5 psi because the FPR and plumbing is much more conducive to flow.

Also, about every 10 psi of FP on this car is worth about .5-.8 of an AFR point. 60 psi wouldn't have solved your lean problem.

So I think it safe to say it's not a fuel pressure problem unless there's something wrong with your electrical or plumbing.

As far as the MAF, you're missing a lot of air to run that lean, assuming that it's metering correctly and the map is right.

With some OBD data logs from that LM-2, we could tell a lot more. You can also get an app for your droid or iphone along with a BT or wifi adapter and log the needed info to help diagnose, FWIW...

Cheers,

Phil
 

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Plug Whisperer
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Makes sense, that is a lot of HP to be making with injectors which are only RC550's. I was wondering how they were getting away with sizing them so small. I am around 265 HP (crank) and (I believe) my injectors are a higher volume part.
Not at all. 440s will make over 250whp just fine, 550s well over 300whp... So it doesn't make sense;)

The Katana kit comes with 440s...

edit: The above figures are quite conservative as well...
 

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Plug Whisperer
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BTW- Here's the OE pump on forced induction.




And here's a 255 on the same power setup, same car.

This is years ago on my car through the stock fuel sender--- before we had surge tanks-eek-:D

 

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Is the MAF stock, and I mean in the stock housing, tubing with air vane? If it is in larger diameter tubing it will read lower air flow and as a result the ECU will be using a different part of the map.

550s will support that much power, but barely. Are they low or high impedance? If low, I don't think a stock ECU will drive them properly.

To really have a diagnosis, you need to log (just like Phil above):

Fuel pressure
A/F (properly calibrated)
RPM
Fuel injector duty cycle or pulsewidth (this will help decide if the injectors are on long enough or perhaps just not flowing fuel - I had a huge problem with the latter recently due to fuel quality and insufficient filtration)

Some other parameters could be helpful, but these basics will tell a lot. Something is fundamentally wrong and I agree, it is not fuel pressure all by itself.
 

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I'll give Jermaine the benefit of the doubt and assume he hadn't had his coffee yet, but that fuel pressure info is bogus.

Stock fuel pressure is ~47 psi and it's essentially static. That said, it 'decreases' as demand for fuel goes up because of a combination of the undersized fuel pump and restrictive pump mount- but it's suposed to be static:rolleyes:

A 255lph pump will typically bring the FP up to about 50psi at idle, but again through the stock system it will decline from there- albeit at a lesser rate than the stock pump would. I have the flow data and actual logs of this on my website from the tests we did back in 2006 or 7...

With our surge tank, if you set it at 47 or 50 psi it will stay there at your power levels +/- 0.5 psi because the FPR and plumbing is much more conducive to flow.

Also, about every 10 psi of FP on this car is worth about .5-.8 of an AFR point. 60 psi wouldn't have solved your lean problem.

So I think it safe to say it's not a fuel pressure problem unless there's something wrong with your electrical or plumbing.

As far as the MAF, you're missing a lot of air to run that lean, assuming that it's metering correctly and the map is right.

With some OBD data logs from that LM-2, we could tell a lot more. You can also get an app for your droid or iphone along with a BT or wifi adapter and log the needed info to help diagnose, FWIW...

Cheers,

Phil
Phil has a point here

The difference in fueling between say 60 psi and 47psi is ~12%. If we take an effective pressure difference at WOT (accounting for the pressure across the injector for boost it would be the difference between 52 psi and 39) it would be about ~15%.

Assuming you have a 15:1 AFR at WOT now the 15% difference in the fuel pressure will put you at ~13:1 which is still too lean.

OP:
While fuel pressure will ABSOLUTELY help, I think you still have another problem there.

You REALLY need to get some AFR data, as well as OBD-II data to diagnose this issue properly. A bluetooth OBD scanner along with a smartphone app would help a ton.

I would be interested in seeing what the computer thinks the air flow coming in is (i.e. MAF), as well as commanded fuel pulse in uS (or duty cycle), and RPM. This data should point you in the correct direction.

If MAF looks low (along with commanded fuel pulse obviously), then it is something in the MAF air metering.
If MAF looks correct, commended fueling is low its in the tune.
If MAF and commanded fueling look correct it is something in the fuel delivery (pump, clogged injectors, injectors too small, etc).
 
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