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Discussion Starter · #1 ·
I installed the REV300tvs kit a few months back and everything seemed perfect with the car. I've had the lotus parked the last few weeks, and then a friend came to visit over thanksgiving so I took him out for a drive in it.

When I last drove it a few weeks ago, the air temperature was around 70 degrees or so. During that time, my A/F was spot on between 11-12.5 : 1 at WOT (depending on load, etc) and it didn't seem to move around much. During that time I didn't experience any strange noises or any hesitation at any RPMs.

This week it's been down in the 30s outside. I let the car warm up for a while to get up to temp, and then took it out for some aggressive driving. Everything seems fine in 1st and 2nd gear (although it blows the tires away so it's hard to notice any engine noises / issues), but when I was on the highway doing 3rd gear pulls, I noticed there was a slight hesitation around 6k rpms. If I go WOT starting at 5k, it will hit 6k, pause for a half/quarter second, and then continue accelerating. When I hit over 7200 rpm or so, the engine tone switches completely and it doesn't sound right at all. It's a hard sound to describe, almost like it switches from the normal engine sound to a high-powered vacuum cleaner.

I also noticed that the a/f ratio has gotten slightly leaner now. When I go WOT, it hits around 13.5 : 1 at first and goes maybe to 12:5 : 1 at higher rpms. When it starts making that noise over 7200, it seems to hit down to 10:1 or so, although it's hard to tell if that's happening when I release the throttle or if i'm bounding off the rev limiter at that point.

For reference, the car is stock besides the rev300tvs w/ koldfire tune and ST muffler. Car has 9800 miles on it.

So my questions are:

1. Would the drop in air temperature cause the car to go leaner overall since it's presumably making more power from the colder air? I have an 05 so there is no AIT sensor to adjust the tune for the colder air. Or does the 30-40 degree drop in ambient temperature not affect the car much once the engine is warm on a non-intercooled car?

2. What could cause that brief hesitation around 6k rpms? The tone of the engine doesn't change at that point, I just noticed that it hangs that for the split second before screaming past it. Maybe a small amount of clutch slip and then it catches at 6k?

3. Any idea why the tone of the engine would change so dramatically over 7k rpms? Could detonation cause a big change in the tone of the engine? Or maybe spark blowout? Or possibly valve float? (although I'm not sure why that would have suddenly happened when it got colder out)

4. What is the actual redline (where it cuts spark) of our engines with a Koldfire tune on the rev300tvs? And what's the realistic redline for our engines with the same setup (where I should shift to stay out of the danger zone)?

Thanks!
 

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Gamera The Atomic Turtle
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I'm an s/c idiot. I'd ask Phil.
 

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You would physically notice spark blow out. It feels like your engine dieing for a split second.

If the Kold Fire software works like Fastworks and is based on load put on the engine (function of throttle and air flow), then you may be hitting an upper part of the map that you don't normally see at higher temperatures. It could just be less refined.
 

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I auto-x my car and hit the rev limiter all the time. Lotus tuned the 2ZZ to hit an 8500 rpm limiter and then after a second, it drops to 8200 or something like that.... it's a two stage limiter. Don't worry about shifting. The ECU protects the motor.
 

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2008 Exige S240
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It is silly to believe 8500 is safe on a routine basis.
These engines with stock heads stop making
power after about 7850 rpms. Past that is only 1-3 horsepower
maybe.
-Robert
 

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Regarding air temp and AFR, if you have no air temp compensation, then yes, the air-fuel ratio will be more lean with lower temperatures. Colder air is more dense, so colder air needs fuel enrichment.

13.5:1 at WOT would make me nervous, esp if the rpm is anywhere near peak torque. Rich and lean do sound different (rich at WOT has a more smooth sound), but the way you describe it, your sound change sounds more extreme than that. Regardless, I would use a light foot until you get this sorted.
 

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What did Phil say? Ask him first...
 

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You need to upgrade your tune. Lots of info here about the limitations of the Kold-Fire tunes.
 

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Discussion Starter · #9 ·
You need to upgrade your tune. Lots of info here about the limitations of the Kold-Fire tunes.
The only thing about changing the tune is that without a temp sensor after the S/C, I wouldn't think a tune would be a permanent fix. If the new tune adds fuel, then when it warms back up then it would have the opposite problem and be too rich. If the software for the tune is completely different, I'm curious how it would handle the extreme cold / temperature fluctuation differently (and exactly what hardware limitation the Kold-Fire tune has that the Fastworks wouldn't).

I don't really drive much during the winter anyways, and it did drive great in the fall for the month or so I had it installed. Not a huge deal if i just need to keep the RPMs down when it's really cold out. Its mostly an overall concern about the big sound change the car makes at the upper RPMs and the slight drop-off in power, and I wasn't sure if it was only temperature related or if there could be another underlying issue there.

I did check the cams to make sure they looked good and I didn't notice any scarring. The only other change made to the car when I started noticing the sound was the installation of a BOE catch can, but I wouldn't think that I would have to get a tune update after installing that.

One other thing... Is it normal to get a slight fuel smell out of the engine bay after installing the catch can with an open breather? I never noticed it beforehand, and I looked all over and couldn't find any actual fuel back there (I've checked after every drive and couldn't see any). I've head a few people mention this particular smell on these engines, so I just wanted to verify that it's normal.

Phil, do you have any input?
 

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Phil sells a TMAP sensor that plugs into your ECU. This allows you to measure intake temp and pressure.
 

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Moldy- Ring me at the shop this week. Please leave a message if we don't answer and I call you back, so that we can visit about what you're experiencing, etc, etc...

Thanks,

Phil
 
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