Hello all,
I've been doing some research to try and understand the differences in the exact capacity on the various generation of the Hyabusa engine in its 1500 iteration but I still fail to understand the exact different in capacity (if there is any) between "long stroke" and "short stroke".
This is some of the information I received from Radical:
Hayabusa 1500:
Gen 2 – long stroke
Gen 3 – short stroke, improved performance, big inlet bodies and big exhaust
Gen 4 – long stroke, improved performance, improved reliability, best of both, big inlet bodies and big exhaust
I have (what I believe to be) a Gen 2 engine which we took apart which has standard 81mm (and I mean standard JE pistons as used by Suzuki) and a 71.5 mm crankshaft... This give me 368.44 cc unit capacity or 1473.76 when multiplied by 4.
Based on this (big IF 🙂 ) does anyone know if stroke and/or bore are any different for other generations ?
Any information in helping me clarify all this will be greatly appreciated.
Thanks,
Nikki
Hi Nikki (@nick02), I can help with pieces of the puzzle. Note that we are referring to Engine generations and should not be confused with SR3 chassis generations
Gen 1 - The PowerTec / RPE Gen 1 1500 was based on the K7 Hayabusa and had a stroke of 71.5MM and a bore of 81mm.
Gen 2 - The PowerTec / RPE Gen 2 1500 was based on the K8 Hayabusa and had a stroke of 71.5MM and a bore of 81mm. The K8 Hayabusa had improved combustion chambers / cylinder heads, titanium valves, more refined camshafts, and improved Life Engine Control Unit (ECU) which resulted in a claimed increase of ~10 HP. These engines had 41mm throttle bodies.
Gen 3 - The PowerTec / RPE Gen 3 1500 was based on the K8 Hayabusa but had a shorter stroke (65mm) and a larger bore (84mm). These engines came with 45mm throttle boddies and larger diameter exhaust. These engines can be identified because they will have an "SS" in the Radical Engine serial number.
Gen 4 - The PowerTec / RPE Gen 4 1500 was based on the K8 Hayabusa and returned to having a stroke of 71.5MM and a bore of 81mm. These cars kept the larger 45mm throttle bodies. I believe they also have the larger exhaust primaries but I have received conflicting reports of this.
Hope this helps,
Charley
Thanks Charlie, that helps quite a bit...
Indeed we are talking RPE Engine Generation, NOT car Generation... 🙂
Are you certain about the bore values though? Particularly in Gen 3, you mention larger bore:
larger bore (84mm)
...but all the other generations are mentioned as the same 84 mm...
Thanks,
Nikki
Thanks Charlie, that helps quite a bit...
Indeed we are talking RPE Engine Generation, NOT car Generation... 🙂
Are you certain about the bore values though? Particularly in Gen 3, you mention larger bore:
larger bore (84mm)
...but all the other generations are mentioned as the same 84 mm...
Thanks,
Nikki
Oops, that was a typo on my part. Gen1, 2, and 4 all have 81mm bore and the gen 3 has the shorter stroke and longer bore. I corrected my first post.
Charley
As Charley says Nikki,
The only things I have to add is that although the Gen 2 Hayabusa engine (Radical Gen 2, 3 & 4) cam with titanium valves they are all removed and replaced with steel.
The short stroke engine (1440cc (Gen 3) vs 1475cc of Gen 1, 2 & 4) also had a few different version of 84mm cylinder barrels fitted. Later/rebuilt ones have a more reliable design but less power.
The 81mm pistons as fitted to the Gen 2 & 4 Radical engines are not JE as standard, Cosworth are. RLM fit JE custom pistons. OEM are not used as with the 18mm L/E pin they fail due to the extreme piston speed!
As Charley says Nikki,
The only things I have to add is that although the Gen 2 Hayabusa engine (Radical Gen 2, 3 & 4) cam with titanium valves they are all removed and replaced with steel.
The short stroke engine (1440cc (Gen 3) vs 1475cc of Gen 1, 2 & 4) also had a few different version of 84mm cylinder barrels fitted. Later/rebuilt ones have a more reliable design but less power.
The 81mm pistons as fitted to the Gen 2 & 4 Radical engines are not JE as standard, Cosworth are. RLM fit JE custom pistons. OEM are not used as with the 18mm L/E pin they fail due to the extreme piston speed!
Thank you very much Dan (and Charley) for this insightful information... That's great information. Much appreciated ! 🙂
Thankyou Charley and Dan for this great information. Do you know what the differences are in the generations of 1340?
Are the 1340's using stock Suzuki pistons, valves etc?
@rlm-dan thanks -- are they basically the same factory long-block -- i.e. everything including camshafts, timing, pistons etc are factory, but the RPE workover is drysump etc?
@proto, Dan can give you a more complete answer, but the short answer is no, they are not the same. The 1340 uses more standard Suzuki parts than the 1500, but Radical has made changes to increase reliability that allow the engines to survive in an automotive environment. For example the clutch basket is beefed up and there are different clearances used for the timing chain to account for the whipping that caused by the paddle shifting. They also use a modified k7 cam chain tensioner on the k8 engines. This is some of the differences, but there are enough changes that make it unwise to go down to the local “Bob’s Hayabusa shop”. Radical does a good job of making upgrades based on the input they get from the the Radical shops. I would strongly recommend only going with a Radical certified shop or RLM ( which has much of the original Radical brain trust).
