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LT4 LT4 hp rating - DIN

1996 LT4 Topic


LT4 hp rating - DIN ?

[NB this message was also posted on the LT4.com forum earlier today]

Hello everyone, strange problem here!

Our local geniuses in the state government of Geneva, Switzerland, have decided that as of 2002, cars here would no longer be taxed on the basis of engine displacement (which was way too easy to determine), but on that of "effective power", appearantly measured according to the german DIN standard (Deutsche Industrie für Normung).

My problem is that they evaluted the effective horsepower of my 96 LT4 Corvette (which I brought back from the States in late 99 and is mostly stock) at no less than 350 hp (257.6 kW) DIN, which is exaggerated in my opinion and way too high for tax purposes anyway (I don't know what conversion method they used, if any; what I know for sure is that they want some US$ 900.- for one year of license plate on that basis, up from $550.- last year!).

So what exactly is the DIN equivalent of the official 330 hp (SAE) for the 96 LT4 Corvette ?

Despite my searching, I have never come across any such DIN hp rating for the LT4. I thought if anyone did, he/she might be reading this board. If this applies to you, please let me know.

Thanks in advance.


NB: I have already filed a complaint against the tax decision, but I can still add elements at this stage. Please note that I am looking for the lowest possible "official" rating here !!!
the only information (official) I have is the factory rating of 330 Horsepower. This was the rating at the flywheel.
Thank you for your reply.

I think that DIN hp is measured further down the transmission line (I don't know where exactly), and that the DIN hp should therefore be lower than its SAE counterpart, not higher like the authority assumed in my case.

Anybody here with a LT4 that's registered in Germany? Did the TüV or any other authority give you a DIN hp rating?

Thanks in advance.

It sounds like Switzerland did some independant testing of engines. While the LT4 is rated by GM at 330hp, it really is close to 350hp.

I'm not familliar with the DIN standard, and as such I dont know where the hp is measured. But if it's like the SAE standard and measured at the flywheel, it should be close to 350hp. If they are talking rear wheel horsepower, then 350 is way out of the question. The best I've ever seen on a stock LT4 is ~300rwhp.

Hope this helps.

ahhh, wonderful Switzerland...

Thank you Jason. Every little bit helps...

Switzerland indeed does independant testing of engines, or has such testing performed by the official importers, in order to ensure that cars comply with Swiss regulations (emissions, noise, etc). Sometimes modifications to the cars are required, even for european models (esp. for noise and lightings). The authorities then issue a Swiss certification sheet for each approved model.

In my case, I do not know whether the LT4 Vette was officially imported and certified in Switzerland; I honestly doubt that it was (probably not worth it for a one-year only model with such a small diffusion). However, my car is a "private import" and was subject to less stringent requirements (I had to demonstrate that I had lived and owned the car abroad for one year minimum in order to be allowed to register it. And I had to have a couple of things modified in the front lights). They even required a technical description from the official GM importer, which cost me $80 for a single sided piece of paper (!) and only indicates that the horsepower is 246 kW (330hp) SAE.

In this case, I guess that the authority does not have a clue about what SAE horsepower is, and preferred to apply an arbitrary displacement-to-horsepower conversion rule, as some fine print in the tax law allows them to do when the horsepower of a particular car is "difficult to assess". As I mentioned today in the LT4 Forum, the burden is now on me to demonstrate that the actual power output of my car is lower than their value.

The reason I am not offering or asking for a rear wheel measure of my car's power is that as you mentioned, the LT4 is conservatively rated at 330 hp. Then I'm afraid that the result would actually be close to 350 hp, if DIN corrected; this would not help against the tax decision. This would also oblige me to remove my B&B exhaust and some other bolt-on mods, which would be a waste of time and money.

I would by far prefer to find some relatively official source that rates the DIN horsepower of LT4 Vettes lower that the SAE rating. So if anyone knows something...



PS: nice GS, Jason...
You could try to contact Gordon Killebrew for this info. He ran the Corvette Action Center at GM for years before retiring. He probably knows more about the C4 than anyone. He wrote most of the service manuals and TSB's for the C4. He now runs a school for the C4 and has a consulting service so he might have the info. His number is 615-654-2864. Good luck.
Glad to be of service Ptidod. I'm surprised that the government will not accept an official document from the GM importer that the car is rated at 330hp. Oh well, no one has ever accused governments of being logical.:D

Thank you for your suggestion, Vetsvette.

I just do not feel very confident calling someone out of the blue in my approximate english... but maybe I'll find the courage.

Anyway thank you for your support, guys, the Corvette community is just great!

After some very quick research on the SAE Net HP vs DIN, they are both Net HP ratings. In other words DIN HP rating is supposed to be the same as the Net which is the American Industry Standard. If the engine power is expressed as kw or Watts the conversion factor(s) are as follows.
KW to HP: xx kW x 1.34 = HP

HP to kW: xx HP x .746 = kW

example: 330 HP x .746 = 246.18 kW

246.18 kW x 1.34 = 329.8812 HP
Obviously the conversion being mathmatical yields fractional results but it's pretty close.

So the bottom line the nearest I can figure, (I'm neither a mathmatician or engineer) is Net HP ratings = DIN ratings.

Are we all confused yet?

Thank you for taking the time to do some research.

Obviously what you found is correct and my own searching indicates that the results of the net SAE and DIN measuring methods are very similar these days (except that we use a 1.36 conversion factor from kW to DIN hp, but that is still very close).

Still 246 kW is a lot for tax purposes and in the meantime I was able to obtain from the official GM importer for Switzerland a paper rating my car's horsepower at a mere 282 hp (207 kW) DIN (!).

I hardly believe that these numbers have anything to do with reality (to the best of my knowledge, they are the same as those of the LT1 F-bodies that were officially imported here), but who cares, the administration accepted that paper as a valid piece of evidence and this will save me over 25% (approx US$ 250.-) off the previous tax calculated on a 257 kW basis.

Now this still represents an increase of 16% (approx US$100.-) compared to their previous displacement-based tax scheme, but I guess I will have to live with that, seems it's a necessary part of the price to pay to have the privilege to drive a Corvette... (I heard of a guy here with a 75 Vette which was taxed at a rate even higher than my 96, and who could get US$500.- off of his tax after specification of the correct hp rating !)

Thanx to you all,

Ptidod'LT4 said:
Thank you for your suggestion, Vetsvette.

I just do not feel very confident calling someone out of the blue in my approximate english... but maybe I'll find the courage.


don't worry, it doesn't take courage...it takes money. Gordon will charge you something like $15 a minute to talk to him. You can be as bold as your wallet will allow.


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