The Lotus Cars Community banner

1 - 18 of 18 Posts

·
Registered
Joined
·
115 Posts
Discussion Starter · #1 · (Edited)
2005 Lotus Elise 8,xxx miles
Blackwatch supercharger install 250 miles ago
5,600 ft above sea level Boulder, Colorado

The problem: I took the car to the dyno (dyno dynamics) along with 4 other supercharges Elises and found out that my car is boosting below all the others with the same SC setups and is fueling very rich.

I was able to test the system with a smoke machine and did not find any visible intake manifold leaks. While “pressurizing” the system smoke eventually came out the intake, I removed the flexible line to the throttle body and plugged the TB with a cap and the system held pressure until the smoke generator could not pressurize any further.

The max boost I was able to achieve was ~5.7psi and the others were around ~7.

Peak HP was at 173 with the others at 204.


Sheet one: 3 runs, all my car (run 15 was stopped mid run I think the O2 sensor fell out and should be disregarded)

Sheet two: My car plotted against the other 2 BWR cars (2006 Elise / 2006 Exige)that were dynoed that day

Sheet three: My 3 HP / Torque graphs from the day

The AFRs eventually got so low the dyno couldn’t log them (it stopped at 10) but on the handheld they went to about 9.6.

Based on the AFRs I’m guessing the supercharger is moving the air past the MAF which explains the low AFRs . I think I’ve ruled out an intake manifold leak with the smoke tester. So where’s the boost going. I have a theory but I’d like to get other’s opinions before I bias the group with my opinion.
 

Attachments

·
Registered
Joined
·
10,000 Posts
belt slip?

Is sheet 1 the same car ? what happened on run 15? why does the AFR get even worse on 16, did something change ?


the blue line/car might have some slip too, even though its more torque, if its the same car thats on the other thread,.
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #3 ·
Is sheet 1 the same car ? what happened on run 15? why does the AFR get even worse on 16, did something change ?

Sheet one: 3 runs, all my car (run 15 was stopped mid run I think the O2 sensor fell out and should be disregarded)

Sheet two: My car plotted against the other 2 BWR cars (2006 Elise / 2006 Exige)that were dynoed that day

Sheet three: My 3 HP / Torque graphs from the day


belt slip?
If the belt was slipping wouldn't the AFRs be more "normal"? I'm assuming the belt wasn't slipping because the MAF was likely seeing the airflow and adding the appropriate fuel. Is this a flawed assumption?

With a slipping belt wouldn't we smell some burning rubber? The motor has low mileage (so the tensioner should be relatively fresh) and the belt is new as well (not much time to stretch).
 

·
Registered
Joined
·
10,000 Posts
I'm assuming your leak test is valid and that there is none, so there isn't much left really, again i'm assuming the obvious stuff has been tested, do you have any other dyno testing/afr of the car before this ?

If the belt slips that doesn't automatically mean the AFR's are right because the airflow is changed, so it'll be in a different area of the map and likely still read the wrong amount of fuel, the math just won't add up.

the boost is relatively smooth , just low, i chatted it over with frank/ronin too, he says the same thing, the amount of slip is going to be about the same, which will translate into a percentage loss. The overalll torque stays the same so whatever is happening is happening consistently.


Plus why are your AFR's so vastly different from 13/14 to 16 ?

If the 02 sensor fell out, i'm assuming these are from a tail pipe sniffer , in which case you're probably 1 AFR unit off, and repositioning it has caused something to go whacky.

I'd imagine 16's AFR is just an entirely bogus read.

But its ridiculously rich, i'd find out whats wrong before i drove it more.
 

·
Registered
Joined
·
115 Posts
Yes, the AFRs were being read at the tail pipe.

So my guess is that the bypass valve isn't sealing properly.

I did notice that the bracket that was holding the bypass valve looked a little tweaked (the bypass valve was resting against the SC housing) when I installed the SC. I tested the linkage and there was no binding and it appeared that it had all of its travel so I assumed that was the way it was intended to be.

Now I'm thinking if the bypass valve bracket is tweaked it may not allow the bypass linkage to to extend all the way, and the valve to fully seal?

What do you think the symptoms would look like if the bypass valve wasn't functioning properly?

What kind of damage could I do with the super rich condition (damage the cat)?
 

·
Registered
Joined
·
10,000 Posts
yeah if the bypass isn't working it could be bleeding boost.

cat damage, flushing the cylinder walls when it ought to be deleaning, spark plug fouling, o2 fouling.

the boost levels should all be the same if everythings working and the same spec cars.
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #7 ·
I need to diagnose the problem so unfortunately I will be driving it a little...

My plan is to hook up a pressure gauge and do some 4th gear pulls to redline so I can get a baseline boost level relative to my gauge (I'm not expecting my uncalibrated gauge to identically match the dyno gauge).

I'll then try to adjust the bypass valve mounting bracket. Hopefully I can get a good look at it from under the car...

Once I adjust the bypass valve I'll try some more 4th gear runs and hope to see a 20-25% increase in boost levels.

If I can see an increase in boost I'll take it back to the dyno and re-check AFRs.

If anyone has any other ways to shady-tree diagnose the bypass I'm very open to suggestions.
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #8 ·
I baselined my gauge and it reads very similarly to the dyno numbers.

I rigged up a flat piece of aluminum to mount the gauge, and tied it into my camera mount. I was able to put the camera on the mount and recorded video of boost and RPMs (my hacked together tell-tale boost gauge).

Now all I need to do is figure out how to adjust my bypass valve without having to remove the entire SC...
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #11 ·
I couldn't get to the bypass valve from the top or the bottom of the car (the top I was blocked by the Supercharger and Intake manifold, from the bottom the starter is in the way). So I have begun the disassembly process.

I made it to the removal of the intake manifold and then realized the fuel rail is in the way of the back middle bolt and I didn’t drain it before I started the project. I’ll be heading to Sears and/or Harbor Freight to see if I can get a heavily offset box wrench or crow-foot wrench to fit in that tight space. If not I’ll bleed the fuel system and “huff” fuel fumes for the next few hours.

I called an Eaton rebuilder and he confirmed the low boost could be attributable to the bypass.

Unfortunately it looks like it may snow here tonight so even if I get it back together tonight or tomorrow I may not be able to test drive it for a few more days.
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #13 ·
I uninstalled the SC last night.

My giant hands really had a difficult time hanging on to the fasteners on the intake manifold as they are tucked away in some tight spaces, it doesn’t help that they’re all stainless so you can’t fish them with a magnet. I managed to drop 3 nuts into the engine compartment and it took me 45 minutes of searching and cursing to find them.

Once I had the SC removed I carefully examined the bypass and it was missing about 10-20% of its stroke. The bracket was tweaked on 2 axis’s. It’s a pretty stout bracket and the bypass is just a plastic canister riveted on so I had to be very careful while straightening it not to damage the vacuum canister.

After some bending, hammering and fidgeting I got the bracket in shape and was able to set it up with the bypass completely closed when it wasn’t under vacuum. I actually set it so the bypass valve spring was slightly preloaded against the butterfly to ensure a tight seal. I then locktited the hardware for the mounting bracket and put everything back together.

After looking at the design I would recommend that anyone installing a new M62 SC check this travel. It’s easy to do and if it wasn’t setup properly from the beginning or if you bracket gets slightly bent in shipping the bypass won’t seal entirely and you will get a low boost situation, like I experienced.

All that being said, I haven’t given the car a test drive yet to make sure I truly fixed the issue but I do think I’ve seen the “smoking gun”. It snowed here last night but it’s supposed to be warm today so I may be able to test my fix tonight.
 

·
Registered
Joined
·
115 Posts
Discussion Starter · #15 ·
I was able to road test the bypass valve fix and I fixed the low boost situation.

Before I worked on the bypass valve it was reaching a max boost of ~5.6psi and now ~7.4psi.

The screen captures of the video aren't the greatest but if you know the first major demarcation is 5ps and the resolution is in 1psi increments you can tell where the gauge is reading.

I also included a picture of the butterfly position before and after I adjusted the bracket.

Overall not a difficult fix for a seemingly troubling problem.
 

Attachments

·
Registered
Joined
·
2,793 Posts
I was able to road test the bypass valve fix and I fixed the low boost situation.

Before I worked on the bypass valve it was reaching a max boost of ~5.6psi and now ~7.4psi.

The screen captures of the video aren't the greatest but if you know the first major demarcation is 5ps and the resolution is in 1psi increments you can tell where the gauge is reading.

I also included a picture of the butterfly position before and after I adjusted the bracket.

Overall not a difficult fix for a seemingly troubling problem.
Glad to hear it Mason, when are we heading back to the dyno? :D
 
1 - 18 of 18 Posts
Top