Dwayne Williams

I recently bought and installed the Lindsey boost enhancer and have noticed that my 951 is now running quite a bit hotter than before (the car is stock except for the LBE). It averages slightly above the first mark and under heavy/long acceleration will get up close to the second mark fairly quickly. I'm wondering if other 951 owners have observed anything similar (particularly those of you in warmer climates like south Texas). The car will cool off fine during "normal" driving and I've checked the usual things (fans, thermostat, coolant leves) and everything seems fine. But the quick heat build-up concerns me. The boost comes up quicker now and since the turbo is running more I would expect a little increase in heat, but not the amount I'm seeing. Anyone else seen anything similar?

Thanks

Jeremy Martin

you're knocking. exhaust gasses get HOT when knocking occurs or you go too lean... turn down the boost, for god sakes turn down the boost! <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />

Dwayne Williams

The LBE doesn't increase boost, it just holds airflow to the wastegate until it builds up 10 PSI. So, the boost level is still stock - it's just available quicker and at lower PRMs than before. So there's no way to dial down the boost.

oi-punx

I was in the same boat as you, only my car wasn't overheating. It was, in fact, registering more boost on the stock gauge than it was previously (.8 bar, around 12 PSI). I emailed Dave Lindsey and was told to turn down the boost on the enhancer to 7-8 PSI because I was running stock chips. I wasn't getting the overboost protection to kick in, but turned it down anyway. Look at the instructions that came with the unit to see how to turn the boost down. There was a thread posted about a month ago that dealt with this topic. You might want to search the archives.

951Tom

Sounds like you've got a cooling system problem. If a stock 951 cooling system can handle a 400+HP motor, a simple LBE addition shouldn't affect your temps at all. Try seeing if bleeding the air out helps.

Russ Murphy

Do you have air in the coolant system? If so, was it there before the boost enhanced runs?
If not, maybe you are getting boost spikes and when thats occurring combustion gases are being forced past the the headgasket into the cooling jacket. Do you smell coolant at all during or after an on boost run? Yours wouldn't be the first 951 to do this.

Jeremy Martin

i know what the LBE does, and you're significantly changing the boost curve from what the dme expects, SO YOU"RE RUNNING LEAN. you're car, not mine. more boost + heat = knock.

special tool

Dwayne - loosen the LBE jam nut and spin the banjo to allow about 2 more threads to become visible. Drive it and see if the heat goes down.

MachSchnell

Jeremy...your comment seems counter intuitive to me...I can appreciate that you're changing the boost curve, but the DME a/f ratios should be programmed based on the AFM data, no? I mean, that would indicate that you'd run more lean with the A/C on, or going uphill, which would be the most ludicrous lack of planning in an engine management system I'd ever heard of. Now, granted, that being said, it wouldn't completely surprise me if Bosch actually was this stupid, but it really seems unlikely that just by adding boost earlier in the curve it would cause the engine to run lean...the amount of boost you make at a certain RPM is a variable amount depending on load, gear, etc, so it should be a value based on the readings of the AFM, not just rpms...please correct me if I'm wrong, I'm just going on what seems logical with how most ecu's interpret boost...

GrantG

Get the Guru chips to correct the mixture,then turn up the boost!

Danno

"my 951 is now running quite a bit hotter than before (the car is stock except for the LBE). It averages slightly above the first mark and under heavy/long acceleration will get up close to the second mark fairly quickly."

The 951 actually has a very, very good cooling system. Last August when I was at Willow Springs and it was 105 degrees-F out! The track-surface was 130-135 degrees! During 20-30minutes sessions of full-on throttle runs, my temp-gauge never went above the 2nd mark (10 o'clock). Then after my runs, I would cruise up to the Balconey and coast back down. By the time I got back to the pits, my car would be nice and comfy at the 1st mark (8 o'clock). So I would say you're generating some serious heat inside the engine to drive the temp-gauge up like that.

I would be very careful about doing some damage. Please review my <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002511" target="_blank">Headgasket dissertation</a> thread. It's actually fairly easy to get a lean high-end mixture at high-RPMs where knock & detonation isn't audible and the knock-sensor isn't reliable (gets washed out by valvetrain & lifter noise).

"The LBE doesn't increase boost, it just holds airflow to the wastegate until it builds up 10 PSI. So, the boost level is still stock - it's just available quicker and at lower PRMs than before. So there's no way to dial down the boost. "

Don't believe the marketing propaganda. The LBE is adjustable, and the pressure that it starts to open is not the boost-level that you'll get; these are two completely different but related values. See this thread for a closer examination of how boost-controllers, wastegate, and boost servo-feedback circuits work: <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=010253" target="_blank">Topic: LBE intalled, getting weird readings </a>

BTW: we calibrate our <a href="http://www.gururacing.net" target="_blank">Boost-Maximizers</a> to start opening at 7psi. Combined with a shimmed wastegate that starts to open at around 7-8psi (depending upon strength of spring), this yields around 15psi on the boost-gauge.

"I can appreciate that you're changing the boost curve, but the DME a/f ratios should be programmed based on the AFM data, no? I mean, that would indicate that you'd run more lean with the A/C on, or going uphill, which would be the most ludicrous lack of planning in an engine management system I'd ever heard of. Now, granted, that being said, it wouldn't completely surprise me if Bosch actually was this stupid, but it really seems unlikely that just by adding boost earlier in the curve it would cause the engine to run lean...the amount of boost you make at a certain RPM is a variable amount depending on load, gear, etc, so it should be a value based on the readings of the AFM, not just rpms"

Ok, let's break this one up. First, all manufactured products have a design target of performance specs. and costs. It would simply be a waste of money to include features and capabilities outside of your design specifications; money that could spent elsewhere. Also Porsche and Bosch are far from gods of engineering what with the thermostat circlip and PLASTIC balljoint cups and all. <img src="graemlins/nono.gif" border="0" alt="[nono]" />

Rather than using black & white, all-or-nothing qualitative blanket statements like 'lean yes/no?', let's look at the variables that are involved and see what happens when you tweak them a little here and there (or a lot in some cases). Please review the algorithm by which the DME arrives at an injector duty-cycle number presented in my <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=002511" target="_blank">Headgasket dissertation</a>.

So here's the conversion table of air-flow meter voltage vs. RPM and the air-flow path at WOT:



An example of staying within design-specs and not wasting time & resources are the flat plateau zones on the far left and far right of the map. These are areas that would NEVER occur in a 951, so their values are fixed at the last allowable value. For example, you would never, ever be able to build up sufficient air-flow at 1500rpm to open the AFM enough to generate a 3.00v signal, so the injector duty-cycle beyond 3.00v@1500rpm is fixed at 20%. Also the MININUM airflow at 6000rpm at the smallest possible throttle-opening would generate at least 2.50v on the AFM, so all voltages below this will generate a 10% duty-cycle signal. Then, all allowable and possible values of AFM-voltages under normal operating parameters have a duty-cycle that corresponds to air-flow.

Taking the comment about air-conditioning, yes it does increase the air-flow, but again we need to examing exactly how much air-flow patterns are changed, not just that, "it has changed and will throw things out of whack". As you can see from the stock air-flow pattern above (orange), turning on the AC at idle does increase the air-flow and that amount can be found on the allowable portion of the map and extra fuel can be dispensed to compensate. Also notice that as RPMs increase and total air-flow volume increases, the extra amount required by the AC yields a smaller and smaller percentage to total air-flow since the load is fairly fixed.

Next, let's look at what happens when you increase the boost on a stock car to 13psi with free-flowing exhaust and intake upgrades (our <a href="http://www.gururacing.net" target="_blank">MAP-sensor upgrade kit</a>). Initial flow patterns are close to stock, however, max-boost at around 3200rpm generates air-flow values that are around 30% higher. As you can see, this maxes out the stock injectors to 100% at around 6000rpm. With our MAP-sensor box, we clamp the air-flow voltage at around 4.6v to prevent driving the injectors beyond 100%. Meanwhile, an unclamped voltage from a stock AFM will cause the DME to arrive at a non-sensical 105-110% duty-cycle. However, further adjustments based upon air-temps and altitude can bring this down below 100%. In any case, we are risking overheating the injectors and DME injector driver-transistor (yes, there's only one). Not to mention the possible damage due to detonation.

Now let's examine the flow-pattern at 15-16psi of boost using the stock flapper-door AFM:



So what happens at 15-16psi? Not only do we max out the injectors at 100%, we max out the AFM flapper-door at 5500rpm. Since the stock table was set up to see maximum air-flow volume at redline at the highest stock-boost possible (with a little leeway), using 40% more boost and 40% more flow than stock would cause this assumed maximum air-flow volume to occur at an earlier RPM. In this case, it's 5500rpm. From this point onwards, air-flow meter volumes stops changing with increased air-flow (as indicated by AFM voltage). There are no more possible injector duty-cycles to look up and the absolute highest value of 128% is used from then on.

The ONLY other variable that's incorporated at this point, is the full-load/WOT fuel-correction map. And with the stock chips as well as all the aftermarket chips we've examined, the correction percentage decreases as RPM increase above 4000rpm. Combined with a fixed AFM-voltage, this would yield less and less fuel as RPMs increase; can we say LEAN??? <img src="graemlins/nono.gif" border="0" alt="[nono]" />

I just realized no one asked Dwayne the important questions:

- what max-boost level do you see on the gauge?
- what kind of chips are you using?

Peckster

I'm running autothority chips with an LBE, and am getting a little paranoid about running hot, although my temp gauge shows normal. I was going to get it dynoed with a report on the exhaust flow, but apparently that doesn't do anything if you have a cat?

Anyhow, my mechanic's going to loan me a gauge with a sensor in the O2 sensor location so I can monitor it for a while to see if I'm running lean anywhere in the rev range. It'll make me feel a lot safer.

Jeremy Martin

Danno, you're one of the best tuners i've ever seen. you have a great knack for explaining things that are somewhat complicated... which reminds me, i'm planning on ordering a custom burn and maybe a maf sometime soon. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
I usually tune cars based off exhaust gas temps and having the temp climb like that probably means the car EGT is running 1000+ degrees, which is 100-200 above where you should be if you're running right (not lean and without knock).
Also, increased exhaust gas temperatures can occur across the range, and not only at WOT. i've seen almost 1000 degrees at partial throttle while running lean... that number should have been 400 degrees, if that.

Danno

."Danno, you're one of the best tuners i've ever seen. you have a great knack for explaining things that are somewhat complicated... "

Why thank you! <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" /> <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" /> <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" /> English IS a foreign language for me, ya know ! So I've had to learn it the 'proper' way through grammar-books and classroom work . That's why I'm always careful to make sure it came across right. The real problem is that I can't type as fast as the words that are forming in my head, and sometimes I leave out complete chunks of a sentence and end up sounding like this: <a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=15&t=011626" target="_blank">Topic: DId they thank?</a>

Dwayne Williams

Thanks to everyone that chimed in on this one. Long story short, I bled the cooling system (little air in there, but not much) and dialed down the LBE to about 7 PSI. Heat problems seem to be gone. Haven't had a chance to look at the chips yet, but will do so as soon as I can.