Decalin instead of TCP?

[Bob Fry]

With the demise of 80/87 avgas, I bought a gallon of TCP and will
start adding that to the 100LL that I must now buy.

However, scouting around the internet I found something that claims to
be similar in function but safer: decalin. Here's a blurb from
Aircraft Spruce. My questions are, has anyone any experience with
both decalin and TCP, and how do they compare? And, in spite of the
last sentance below, can decalin be used beneficially in certified
aircraft engines?

"Scavenges Lead in aviation fuel after combustion to prevent lead oxide
buildup on valves but still allows the lead to perform the anti-knock
function prior to combustion.

"It is an excellent additive for auto conversions, where it reduces
buildup on oxygen sensors and plugs. If you have to use 100LL, then
this stuff is for you. Prevents valve seat erosion from valve seat
micro welding. It is equivalent to TCP.

"Does not contain volatile solvents so it is safe to ship and safe in
the cockpit. You can carry it with you for out-of-town airports.

"Easy to use graduated measuring and dispensing resevoir built into the
bottle. No messy syringes!

"Tested and stable down to 0 degrees F.

"Decalin TCP is not approved for use in the engines of certified
aircraft."

[tony roberts]

At Arlington the Aircraft Spruce salesman told me to watch for a new
product that was reputed to be better than TCP (a mute point really as
nobody can find TCP for sale). So maybe this is it.
I can't comment on Decalin but I can pass on one piece of information
that many don't know. TCP themselves, and many knowledgeable sources,
all say that you should never use TCP in a higher than 1000 TBO engine.
NTSB reports site TCP (and MMO) as causes of accidents in high time
engines, where crap has been dissolved/dislodged, and has then managed
to stall an engine.
I mention this just because I believe you should check if Decalin
suffers from the same problems.

HTH

Tony
C-GICE

In article >,
Bob Fry > wrote:

> With the demise of 80/87 avgas, I bought a gallon of TCP and will
> start adding that to the 100LL that I must now buy.
>
> However, scouting around the internet I found something that claims to
> be similar in function but safer: decalin. Here's a blurb from
> Aircraft Spruce. My questions are, has anyone any experience with
> both decalin and TCP, and how do they compare? And, in spite of the
> last sentance below, can decalin be used beneficially in certified
> aircraft engines?
>
> "Scavenges Lead in aviation fuel after combustion to prevent lead oxide
> buildup on valves but still allows the lead to perform the anti-knock
> function prior to combustion.
>
> "It is an excellent additive for auto conversions, where it reduces
> buildup on oxygen sensors and plugs. If you have to use 100LL, then
> this stuff is for you. Prevents valve seat erosion from valve seat
> micro welding. It is equivalent to TCP.
>
> "Does not contain volatile solvents so it is safe to ship and safe in
> the cockpit. You can carry it with you for out-of-town airports.
>
> "Easy to use graduated measuring and dispensing resevoir built into the
> bottle. No messy syringes!
>
> "Tested and stable down to 0 degrees F.
>
> "Decalin TCP is not approved for use in the engines of certified
> aircraft."




--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE

[Paul Sengupta]

"tony roberts" > wrote in message
news:nospam-298825.23052207092004@shawnews...
> TCP themselves, and many knowledgeable sources,
> all say that you should never use TCP in a higher than 1000 TBO engine.
> NTSB reports site TCP (and MMO) as causes of accidents in high time
> engines, where crap has been dissolved/dislodged

TBO or SMOH? What about if you've been using it from the start?

Paul

[Corky Scott]

On 07 Sep 2004 20:39:22 -0700, Bob Fry
> wrote:

>"It is an excellent additive for auto conversions, where it reduces
>buildup on oxygen sensors and plugs. If you have to use 100LL, then
>this stuff is for you. Prevents valve seat erosion from valve seat
>micro welding. It is equivalent to TCP.

I am not a internal engine combustion expert, and don't play one on
TV, but I have a couple of thoughts to add regarding this statement:

The auto conversions I'm aware of tend to run cleaner than certified
aircraft engines regardless whether they are carburated or fuel
injected. This is because they normally run with a mixture closer to
the stochiometric ideal than do the aircraft engines during the
settings other than leaned for cruise.

Most auto engine conversions do not have fixed timing. The timing
adjusts as need be for the running condition. Some of them are using
full fledged auto fuel injection and timing computers which vari the
timing and fuel being injected many times a second according to the
sensors. With the full boat conversions, those using all the sensors
and computers, the timing and fuel mixture adjusts for all situations,
including altitude compensation. Unlike fixed timing engines, this
means the engines never get to the point where the peak pressure point
approaches top dead center where the pressure increase can cause
detonation at high power settings, because the computer keeps the
timing adjusted to prevent that. Tixed timing engines MUST use the
richer mixture for high power settings in order to retard the
mixture's rate of burn so that the PPP does not occur with the piston
at TDC. The rich mixture burns more slowly than a mixture that is
close to ideal.

With all this in mind, the auto conversions tend to run leaner
mixtures most of the time which ,(this is where opinion raises it's
head) should reduce lead buildup in auto conversions. Why? Because
the nearly ideal mixture ratio results in near complete combustion.

That's the way it looks to me anyway.

Corky Scott

[Ron Wanttaja]

On Wed, 08 Sep 2004 12:49:14 -0400, Corky Scott
> wrote:

>On 07 Sep 2004 20:39:22 -0700, Bob Fry
> wrote:
>
>>"It is an excellent additive for auto conversions, where it reduces
>>buildup on oxygen sensors and plugs. If you have to use 100LL, then
>>this stuff is for you. Prevents valve seat erosion from valve seat
>>micro welding. It is equivalent to TCP.
>
>I am not a internal engine combustion expert, and don't play one on
>TV, but I have a couple of thoughts to add regarding this statement:
>
>The auto conversions I'm aware of tend to run cleaner than certified
>aircraft engines regardless whether they are carburated or fuel
>injected. This is because they normally run with a mixture closer to
>the stochiometric ideal than do the aircraft engines during the
>settings other than leaned for cruise.
>
>Most auto engine conversions do not have fixed timing...
[SNIP]
>
>With all this in mind, the auto conversions tend to run leaner
>mixtures most of the time which ,(this is where opinion raises it's
>head) should reduce lead buildup in auto conversions. Why? Because
>the nearly ideal mixture ratio results in near complete combustion.

Corky, do the computers that adjust the timing use the O2 sensors in the
exhaust? If so, they're probably getting hosed up when leaded fuel is
used. But if you're *not* using 100LL, you don't *need* TCP....

Ron Wanttaja

[tony roberts]

> TBO or SMOH? What about if you've been using it from the start?

At 1000 hours they are both about the same :):):)
The advice I got was not to START using it on a mid to hightime engine,
because of existing buildups which can dislodge.
If they have been used from the start, and performed as advertised there
shouldn't be any buildups. But personally I would ask the manufacturer
first.

Tony




--

Tony Roberts
PP-ASEL
VFR OTT
Night
Cessna 172H C-GICE

[Morgans]

"Ron Wanttaja" > wrote

> Corky, do the computers that adjust the timing use the O2 sensors in the
> exhaust? If so, they're probably getting hosed up when leaded fuel is
> used. But if you're *not* using 100LL, you don't *need* TCP....
>
> Ron Wanttaja

It is my understanding that the O2 sensor is not important to the system,
while running at wide open, or near wide open throttle. When the O2 sensor
is hosed, the engine will run in the rich, limp home mode, only at low power
settings. Not an issue, as long as it keeps running at idle, when the power
is pulled back, no?
--
Jim in NC


---
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[Bruce A. Frank]

Corky,

Bud just overhauled the heads on his Ford because it sat for a number of
years in Florida. He has been using 100LL almost exclusively. The head
shop found heavy lead deposits on the valves which they found difficult to
remove (probably forgotten how). It may be that TCP or similar product is
necessary in our Fords if we run avgas all the time.

Corky Scott wrote:

> On 07 Sep 2004 20:39:22 -0700, Bob Fry
> > wrote:
>
> >"It is an excellent additive for auto conversions, where it reduces
> >buildup on oxygen sensors and plugs. If you have to use 100LL, then
> >this stuff is for you. Prevents valve seat erosion from valve seat
> >micro welding. It is equivalent to TCP.
>
> I am not a internal engine combustion expert, and don't play one on
> TV, but I have a couple of thoughts to add regarding this statement:
>
> The auto conversions I'm aware of tend to run cleaner than certified
> aircraft engines regardless whether they are carburated or fuel
> injected. This is because they normally run with a mixture closer to
> the stochiometric ideal than do the aircraft engines during the
> settings other than leaned for cruise.
>
> Most auto engine conversions do not have fixed timing. The timing
> adjusts as need be for the running condition. Some of them are using
> full fledged auto fuel injection and timing computers which vari the
> timing and fuel being injected many times a second according to the
> sensors. With the full boat conversions, those using all the sensors
> and computers, the timing and fuel mixture adjusts for all situations,
> including altitude compensation. Unlike fixed timing engines, this
> means the engines never get to the point where the peak pressure point
> approaches top dead center where the pressure increase can cause
> detonation at high power settings, because the computer keeps the
> timing adjusted to prevent that. Tixed timing engines MUST use the
> richer mixture for high power settings in order to retard the
> mixture's rate of burn so that the PPP does not occur with the piston
> at TDC. The rich mixture burns more slowly than a mixture that is
> close to ideal.
>
> With all this in mind, the auto conversions tend to run leaner
> mixtures most of the time which ,(this is where opinion raises it's
> head) should reduce lead buildup in auto conversions. Why? Because
> the nearly ideal mixture ratio results in near complete combustion.
>
> That's the way it looks to me anyway.
>
> Corky Scott

--
Bruce A. Frank, Editor "Ford 3.8/4.2L Engine and V-6 STOL
Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|

[Corky Scott]

On Thu, 09 Sep 2004 06:49:10 GMT, "Bruce A. Frank"
> wrote:

>Corky,
>
>Bud just overhauled the heads on his Ford because it sat for a number of
>years in Florida. He has been using 100LL almost exclusively. The head
>shop found heavy lead deposits on the valves which they found difficult to
>remove (probably forgotten how). It may be that TCP or similar product is
>necessary in our Fords if we run avgas all the time.

Well, there you are: actual experience trumps conjecture most of the
time. I humbly bow to the superior information.

Ron, as to the oxygen sensor, some very clever people have managed to
fake out the system by sending a trace voltage to the computer making
it think the sensor is working. Don't know how the computer then
knows how to adjust for all conditions when the signal to the computer
from the O2 sensor is fake though.

Having to fake out the computer, along with having to depend on the
single source for your ignition AND timing is why I've chosen not to
go that way. Well, that and not wanting to pay for injection capable
heads and the fuel pump, rails, plumbing, injectors etc etc for a fuel
injection system.

Corky Scott

[Richard Tasker]

Go ask this question on: . That is where the idea was conceived by Chris Lowery to formulate a substitute for TCP - which is chronically in short supply. He is a
chemist by trade and saw a need for the group (using Subaru engines which normally like autogas).

Dick Tasker

Bob Fry wrote:
> With the demise of 80/87 avgas, I bought a gallon of TCP and will
> start adding that to the 100LL that I must now buy.
>
> However, scouting around the internet I found something that claims to
> be similar in function but safer: decalin. Here's a blurb from
> Aircraft Spruce. My questions are, has anyone any experience with
> both decalin and TCP, and how do they compare? And, in spite of the
> last sentance below, can decalin be used beneficially in certified
> aircraft engines?
>
> "Scavenges Lead in aviation fuel after combustion to prevent lead oxide
> buildup on valves but still allows the lead to perform the anti-knock
> function prior to combustion.
>
> "It is an excellent additive for auto conversions, where it reduces
> buildup on oxygen sensors and plugs. If you have to use 100LL, then
> this stuff is for you. Prevents valve seat erosion from valve seat
> micro welding. It is equivalent to TCP.
>
> "Does not contain volatile solvents so it is safe to ship and safe in
> the cockpit. You can carry it with you for out-of-town airports.
>
> "Easy to use graduated measuring and dispensing resevoir built into the
> bottle. No messy syringes!
>
> "Tested and stable down to 0 degrees F.
>
> "Decalin TCP is not approved for use in the engines of certified
> aircraft."
>
>