Vanilla Lycoming vs. Thunderbolt?

I'm beginning to think seriously about engine options (I can already taste the OSH special...) and I've been wondering whether the Thunderbolt is worth its premium over the standard Lycoming.

When I built my -8 so many years ago, I ordered an IO-360 from Aerosport Power and was very happy with both the engine and the service that I received from Bart. I ordered one Lightspeed EI and Airflow Performance FI and paid, as I recall, $25K.

Aerosport's price today for an IO-390 is north of $41K vs. Van's price of $35K with one EI (less the prop discount and any further show special). Van's Thunderbolt price is $38.6K with one EI (less the same discounts previously mentioned).

So, assuming that I don't care about pretty colors on an engine that (hopefully) almost nobody will ever see, why does the Thunderbolt merit a $3K+ premium? I understand that the components are balanced to a greater degree than the standard Lyc, but it can't be that much smoother, can it? Really?!?

Naturally, I'm not trying to start a war and I'd rather not provoke anybody's confirmation bias, but I'm definitely open-minded about it and (as always!) willing to be taught something new. Have at it, boys...

My first engine from Lycoming was a Vanilla flavored and it ran like a Japanese watch, even better than a switch watch.
I was all set to get the same and spend the $3+K on other things. After talking with a few people, especially Jeff at Lycoming, I was made to believe that it may be worth the extra $3k. After all, what is $3K when my panel alone is worth a used Cessna.

Some of the selling point has been,
- Tighter tolerance and balance
- Only two people build them, so closer attention
- Polish ports translate to more HP
- Nicer looking paint (like you I care little about this)

Same crank, same balance. Recip components matched to 1/2 gram.

The port work is more about flow balance than max power. There is some flow variation between stock cylinders.

Don't minimize recip components weight matching. The outside of a crank counterweight is a lot closer to the crank center line than the top end of a piston/pin and the small end of the con rod. Matching the weights of the mass fartherest away from the crank center-line is the most critical.


I don't know what the Thunderbolt process entails but all the magic in power production is in the induction system so the intake runners are a big part of the game. If they do not put the heads on a flow bench after their modifications to see what they have done something is wrong.

vernon smith said:

Don't minimize recip components weight matching. The outside of a crank counterweight is a lot closer to the crank center line than the top end of a piston/pin and the small end of the con rod. Matching the weights of the mass fartherest away from the crank center-line is the most critical.


I don't know what the Thunderbolt process entails but all the magic in power production is in the induction system so the intake runners are a big part of the game. If they do not put the heads on a flow bench after their modifications to see what they have done something is wrong.

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You can balance port flow in the heads all you want but if you bolt up some of the stock intake manifolds, it's all pretty much wasted as we know from testing with EFI. There can be some pretty dramatic flow differences between cylinders from the intake as well as differences in primary exhaust tube length. Flow benching heads is about 1/3rd of the equation in the quest for equal airflow between cylinders in a running engine.

Luck of the draw

It really is the liuck of the draw on the assembly-line engines. You may end up with a smooth one or you may end up with one that is not so smooth. With the Thunderbolt, everything is matched up with a lot of personal attention (the same for Barrett, Mattituck, etc).

It's the same reason we build our airplanes--- they, too, get a lot of personal attention during construction, unlike an assembly-line airplane.

I can tell you that 200+ hours into my Thunderbolt engine on the RV-10 in a year, it was worth every penny.

That being said, the Van's O-360 in my RV6 never missed a beat in it's 1800 hours until it had a prop strike. But if I were to build another 6/7 etc, it would get a Thunderbolt. I can tell a difference. You have to decide if it is worth it to you.

Vic

The value of recip parts balance ?

I have two engines dynamically balanced as well as AircraftSpecialty?s shop is capable. The recip components are all matched to Zero gram variance within the repeatability tolerance of the scale used. That said, I wonder about the affects of carbon and lead deposits on the piston assembly weight match over time. I have no idea if the deposit build up is significant or not. If yes, the extreme balancing is just psychological gratification. Apparently 1/2 gram is validated to be as good as practical considering the other factors affecting ?smooth?.
Referencing Ross?s point about cylinder charge variance, where does balance fit on the comparison scale with power pulse variance on a low RPM Lycosaurus ?

A 3 gram tolerance on Lycoming piston or rod weights would be imperceptible to the pilot. I used to balance auto race engine parts to .5 grams and these had much lighter parts and turned about triple the rpm as a Lyc. As a % of total assembly weight, such tolerance is not needed in a Lycoming.

There would be far more vibration set up by airflow imbalance between cylinders where we've seen a 10% variation in one instance. This means you might see one cylinder putting out 10% more power than another as a worst case.

If you want smoothest running, a proper manifold and near equal length exhaust headers are far more significant.

i have had one of each. the first went way past tbo and started making metal on the cam/lifter. very happy there.
the second was a thunderbolt with flowed heads and roller lifters. about 26k back in 07. running a carb on both the tbolt engine can be leaned without any roughness. both as smooth as can be. prop balanced on both setups.
i will past the 5,000 mark on the trip north next week. rvs rule the sky.

DanH said:

Same crank, same balance. Recip components matched to 1/2 gram.

The port work is more about flow balance than max power. There is some flow variation between stock cylinders.

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Dan,
Do you still feel that they are fairly comparable? The lead time on the Thunderbolt is 3 years. I am not sure I want to wait that long. I can get the stock motor in 6-10 months and 13K cheaper. Thoughts?

I've got an rv14 builder friend asking the exact same question right now. I'm hoping to talk to Lycoming at osh and get some more detailed answers. An extra 2.5 years and 12k seem like way too much for what the thunderbolt offers (better balance, port/polish , and paint). Plus the vanilla lyc and the thunderbolts advertise the same HP rating, so while it might be a touch smoother, you're not getting anymore peak power out of that cash.

kbalch said:

Van's Thunderbolt price is $38.6K with one EI (less the same discounts previously mentioned)...

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It’s been 5 years since this was written. Ouch….
Granted the new price has dual Pmags but my paycheck never saw this kind of pace.

I would go with the EXP119 hands down.

If I you to have the Thunder bolt features, check with Barrett for price and delivery time