Paul, in the past, turboed engines often had low compression pistons to alleviate detonation problems.  These ratios were commonly in the 8:1 and sometimes lower.  When turbos were removed/disable from these low compression engines, they were indeed “dogs”.  However, the rotor’s compression ratio (at least on the later model 13Bs) have always been around 9:1  or above and as Tracy pointed out the N/A engines were only a few point more.

 

I have been flying with a turbo block (sans turbo)  for a number of years.  I pick the turbo block because it did not have the exhaust splitters as in the N/A block which some believe knocks some power off (I know of no factual evidence to support this).  I did however, replace the 9:1 turbo rotors with 9.7:1 “high compression” N/A rotors.

 

My perceptions is that this engine has more power – but, that is probably more because of improvements to the induction system that block choose or compression ratios.

 

 A downside of using a turbo block without the turbo is the exhaust.  According to Mazda test, the splitters in the N/A engine knocks 8db from the exhaust.  I know for a fact, that without muffler the turbo block pegs a sound meter at 125 db.  Also the pulse is so strong it can destroy stainless steel by fatiguing it past its failure point.  I squeeze the ends of my exhaust tubes and drilled holes in them early on to try and team this Noise Monster and found that after a 15 minute flight the shock wave of the exhaust had fatigued them to the point that chunks the size of my thumb nail were cracked off and gone.

 

I found the turbo block easier to street port than the N/A 13B because it didn’t have the aux port in the block, but that’s about it.

 

 

 

 

 

To Everyone—

                We have both a 13b  NA (unknown vintage—80’s?) and a ’91 Turbo 13B engine and are just beginning their teardowns, both allegedly running but internal condition unknown.   Would there be any problem running the Turbo engine (BUT NOT with the turbo setup-- AS IF it were a NA engine)?  Is it a “stronger” engine than the NA?  Would it need a different Timing setup?  Would there be a compression problem running it sans turbo? (Hearsay has it that it would be a “dog”.)  If some of the individual parts spec out to be better in one engine but not in the other, would there be any problem/advantage in “mixing & matching” the various parts in the newly built up engine, i.e., rotaries, side plates, eccentric shaft, etc?   We would appreciate your inputs.    Thanks!

 

Paul & Don Vermillion

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