posted on September 08, 2013 13:31
The Heart of a Record Breaker Part I: Enter the SR15VET 20V
In the last three years, it seems that I've said it over a thousand times. When it comes to land speed racing, take most everything you know about racing and throw it away. There are so many generally accepted practices in motorsports and preconceived notions about racing that just don't apply when it comes to land speed racing. In fact, much of the time these common practices are the polar opposite of the practices standard to that of building a car for Bonneville. Land speed racing is the realm of motorsports where lead weights are added to cars, wide tires are replaced with skinny ones, and the thought of replacing the factory brakes with an exotic multi-piston brake kit is considered to be a foolish investment.
After smashing just about every record in the "G" and "F" engine classes, Doug and Miriam Macmillan of Team Hondata decided to build a de-stroked K20 (K15) so they could claim a whole new set of records.
In the same sense, where most racers would consider changes in displacement only in one direction (larger), the land speed racer will do whatever it takes to set a land speed record even if it means decreasing an engine's displacement. Why did we choose this route though?
Project 240SX LSR's class was first questioned during tech inspection. After we politely disagreed with the tech inspector the question was then elevated to the SCTA, who officially classified the car as "Production."
Winston Churchill once said, "Seize the opportunity in every difficulty." Well, our difficulties started while going through tech inspection during the last race of the season at El Mirage. See, up until that point we had been chasing the G-BGC (1.51 L to 2.0 L Blown, Gas, Coupe) record. And, one of the stipulations to run in that particular class is an engine swap. No problem right? We swapped an SR20DET into a 240SX. Wrong! Apparently, in the eyes of the SCTA we essentially just recreated a Japanese spec car (a late model 180SX). Long story short, this placed us back in the Production class… where the record was over 226 MPH! Shit.
Producing over 900 WHP, the Raver Motorsports Mitsubishi Galant VR4 has set G/PS records in excess of 220 MPH at both Bonneville and El Mirage. Photo courtesy of Vernon Brunges.
Here's where "seizing the opportunity in every difficulty" comes into play… although I would like to think of it as shear brilliance. The record in the production class for a 1.51 L to 2.0 L was 226 MPH by an AWD Galant and the other an AWD Audi. The Production class is the only place an AWD car is allowed to compete since it provides such a distinct advantage. However, for a 1.0 to 1.5L engine, the Production class record remained a more reasonable 167 MPH at Bonneville and 135 MPH at El Mirage. Inspiration! We'll simply reduce the SR20DET's displacement. Necessity is the mother of invention isn't it?
Look at the miniscule distance between TDC and BDC. This surely isn't 86 MM of stroke!
Removing 25% or one cylinder's worth of displacement from an engine is easier said than done though. My first instinct was to have some custom sleeves made to decrease the bore to 83.0 MM and use an SR16VE crankshaft with 68.7 MM of stroke. It seemed easy enough, but there were actually many complications and disadvantages that came along with it. The result of de-boring the cylinders would leave a step where the 86mm diameter combustion chambers met the smaller 83.0 mm bore sleeves. This wasn't exactly ideal for the translation of combustion pressures into the rotating assembly. Also, this mismatch in diameters would require that notches be machined into the smaller sleeves to ensure proper valve clearance and even then the flow would most likely be shrouded by the smaller diameter bores. And what about the head gasket? These were just a few of the challenges… It was time to focus our attention on modifying the crankshaft instead.
Monday, September 09, 2013 1:56 AM
This is so cool and trick!!!!
Does it have a realllly high rev limit now!?
Monday, September 09, 2013 10:05 AM
We've only tuned it up to 8,600 RPM but are not done yet. It all depends on where the power starts following off. In other words, no sense in beating the piss out of it if its not making more power. Glad you enjoyed the article. The next one will go even further in depth covering more of the parts and Nick Hunter's Hunter's assemble of the engine.
Monday, September 09, 2013 10:27 AM
I´ve been waiting for your article. We currently race in a class where we can either use a turbo 1.43L or a 2.0 NA and wanted to know how you had handled the destroking. We are using a SR20VE and I´m in the process of specking everything.
I´m really interested in Castillo´s services. If could send me by email (email@example.com) Castillo´s contact details and maybe aprox cost and lead times.
Monday, September 09, 2013 10:39 AM
i honestly think that there's more than 600WHP trapped in this little engine! i also believe that (taking common sense and pitching it out the window) this engine could do in the 9500 ballpark, although, the crank would probably crack!
one thing IS clear, based on the little bit of time spent on the dyno, the turbocharger on this engine is capable of FAR more than I ever anticipated! i doubt we will run into that issue where the turbo is turned up to 11 and we are looking for 12!
stay tuned :)
Monday, September 09, 2013 11:10 AM
So what were you guys looking at in the class that didn't allow your "engine swap"? I'm sure there are plenty of engines you could put in a S13 under 2.0L. My favorite being a 4G63T. There's at least a couple swaps floating around and it could easily meet your power goals and likely fit into that swapped class.
Monday, September 09, 2013 11:30 AM
As to the question "Is there a point when a rod ratio is too high?", it depends on a lot of things. Since rod-to-stroke ratio affects dwell time and piston acceleration, it comes down to how much RPM can your bottom end and valvetrain handle without grenading itself, and what octane of fuel are you running. In an engine with a very low rod-to-stroke ratio, there is very little dwell time, and very quick piston acceleration away from TDC, which means at high RPM, the piston will start to outrun the flame front, and you just won't make any more power. I suspect that this may be why some modern engines can get away with running regular grade fuel in spite of high compression and/or turbo charging. So running a very high rod-to-stroke ratio will enable you to make more power at higher RPM, but it doesn't help you if your engine can't spin that fast. A rod-to-stroke ratio of 2.4:1 is approaching Formula 1 territory, and if you can design the bottom end and valvetrain to handle 15,000 rpm....my hat is off to you! I'd be interested to see what it is capable off!
Monday, September 09, 2013 12:42 PM
Oh Chucky, how you tease us so. HOW MUCH POWER!!?!??!111!!!? :)
Monday, September 09, 2013 1:37 PM
Has the engine been dyno'ed in its "original" form? It seems like for the original SR20 you were making 350ish hp and did 180. Now you went 180 with the new motor so can we assume it is making hp in the mid 300's?
If that is the case and Nick thinks it can spin 600 I wouldn't doubt that 200+ mph is just around the corner.
The class you are in doesn't allow for major aero mods right? Are there "stock" 180sx mods that can help keep the car from squirming?
Monday, September 09, 2013 3:12 PM
Other than price, how can you tell if a custom crankshaft is good quality or not?
Besides metalurgy, how can a crankshaft be checked for defects after purchase?
What kind of processes can be undertaken to strengthen a crankshaft if you are not satisfied with the product?
Monday, September 09, 2013 3:17 PM
Just spoke to Joe Castillo and I think I will use his shop for our crank.
Thanks again for the article and hopefully you can shed more light on all the special parts you used on your build.
Monday, September 09, 2013 3:43 PM
I enjoyed meeting your team on the salt. I'm very glad that the gremlins were fixed and you were successful. Some day I'd like to know what was the issue, the MAF, some other electrical gremlin?
I do enjoy the creativity you see at Bonneville. It's one of the few places that still allows it.
Best of Luck
Monday, September 09, 2013 8:54 PM
@protodad I’m not sure what you mean by “original form” but we’ve made much more than 350 hp on the dyno… although I’m not going to divulge exactly how much yet. Just know that it was much more We ran out of time to really optimize boost management so at Speed Week you’re HP estimations might be close… or they might be off, lol.
@jose cabra glad to hear that you got a hold of Joe. He is truly a great guy and I have yet to meet anyone who knows more about crankshafts than he does. Last time I spoke with him, he was telling me in intimate detail the direction that each journal bends after being machined. He’s like the crankshaft whisperer or something.
@jeffball610 We really didn’t consider swapping to other engines so we could stay in blown gas coupe. A part of the reason would probably have to do with the expense of fabricating all the mounts and then dealing with the wiring. Probably the larger reason was the experience that my team has with Nissans. We probably have some of the most knowledgeable Nissan gurus in country in our corner. Throw in the spare parts we have lying around and it just made sense to stick with an SR20 based platform.
@Bob Holmes It turned out to be our 20 year old ECU.
Monday, September 09, 2013 9:12 PM
@awdu13 that’s a really tough open ended question but I’ll take a shot at it and maybe someone else will have some more input to add.
Aside from a visual check looking for any type of aesthetic flaws, there is not much you can do without the proper tools. If you can get a hold of a micrometer, height gauge, indicator, and a set of V-bocks you could inspect the journal diameters as well as roundness and/or cylindricity. With a height gauge and set of v blocks you might also be able to check overall straightness of the crankshaft. You could take the data you collect from these inspections and compare them against the specs stated in the FSM. If something is out of whack there you could most likely have it fixed by a crankshaft shop.
These inspections only scratch the surface though. I mean you could have all sorts of issues ranging from the alloy type to bad heat treating. Does the average guy have a hardness tester or can he afford to sacrifice one crankshaft to section and send out for a material analyses? And this isn’t even getting into the design portion.
How do you verify that the design is correct? Invest in a FEA package to verify the design and a dyno cell to validate the design in its actual environment? Man this gets hairy quick doesn’t it?
I think at the end of the day this question you ask is the very reason why a company’s reputation is so critical. I’d hate to say go off of word of mouth but I’d definitely suggest performing your due diligence on the research side of things. If all else fails, take it to a guy who eats, shits, and breathes [insert component here] and get his opinion. I hope that helped a bit. Good question.
Monday, September 09, 2013 9:20 PM
@sethulrich- good feedback. I'd like to add one point to that. I think direct injection systems are a very significant reason why many of today's small displacement, turbo charged engines can run high CR on pump gas. I'm not sure if the rod ratios are really that great of a factor but i haven't looked far enough into it because I pick old cars to race due to their affordability, lol.
Monday, September 09, 2013 10:00 PM
That crank work is amazing... never knew it could be modified in such a fashion.
Monday, September 09, 2013 10:31 PM
You obviously didn't read Project MR2 back in the day in SCC!
Wednesday, September 11, 2013 12:37 AM
@Chuck Johnson - Agreed! Direct injection does significantly aid in that. I don't know how much influence the rod-to-stroke ratios have on the ability to run lower octane, but I have just observed a trend that seems towards lower rod-to-stroke ratios (along with a trend towards undersquare bore-to-stroke ratios). That trend may be as much be driven by engine down-speeding and downsizing, to maximize the low end torque of a smaller engine.
Wednesday, September 11, 2013 10:45 AM
Great article! Since you're a piston guy, can I ask about ring packages with your motor? I didn't notice any gas ports, just an accumulator groove. I did notice that the bores were pretty smooth too. Thanks Chuck!
Thursday, September 12, 2013 12:52 AM
check out the link below for a in depth explanation on the ring set I used. This is from the long rod build article Mike and I wrote a few years ago but the ring set is still the same.
Regarding the gas ports, it's not very common to see gas porting on a piston for a turbo charged engine. The only times that I've really seen it is on some all out drag motor that will see a limited amount of cycles. Gas porting is really hard on the face of the rings and with the increased cylinder pressures associated with forced induction is even harder. Yes, in theory it creates a better seal allowing gas pressure to act on the backside of the ring forcing it into the cylinder wall; however, it will wear down the face of the ring down faster. Since our engine will see a lot of cycles with all of the dyno time and multiple 5 mile runs, we opted on the side of durability over a few extra ponies. Besides, we can just turn up the boost!!!
Thursday, September 12, 2013 9:02 AM
Hi Chuck since you are the piston expert I was wondering what modifications or alterations would you make to make these pistons as reliable as possible.
We run some 6 hour races and need these to be as bulletproof.
Thursday, September 12, 2013 4:00 PM
I don’t think that I would change much from my piston design for your application. Honestly, I feel like this piston is pretty much on the conservative side.
I crunched some quick numbers and it looks like to net 1422 cc’s of engine displacement you need a 86.5 bore x 60.5 stroke. (I always allow for .5mm over bore for repair.) With this in mind, the one thing that will have to change on the piston for you is the pin height. Using a 8.318 block height, K1 H22 rod of 5.636”, stroke of 2.382” and a deck clearance of .005 your pin height will be 1.486. This is pretty damn tall and I’m honestly not sure if it will fit on JE’s asymmetrical forging. I think our 1.427” pin height design barely fit on it. You could switch to the longer F20 rod that I mentioned in the article, but even with the H22 rod you rod ratio is at 2.36. Maybe you can deck the block a bit and look into using the F22 or F20 rods?
Also, with such a tall pin height there is a lot of weight naturally trapped in the part (above the pin bore itself). You will need to invest in a 3D undercrown milling to reduce the piston mass to manageable place. Ours was just over 400 grams which is about 80 grams or so heavier than the typical SR20 piston. This is even with the 3D undercrown milling.
Lastly, if you're going to reference my design, you would have to change the valve relief diameters for your size valves. Mine were made for 1 MM over I believe.
Thursday, September 12, 2013 4:41 PM
on your article you said you could have a pin height of 0.966 for a regular sr20ve and H22 rods.
I calculated I could use F20C rods, a 60.5mm stroke, and a custom pin height of 1.14 inches. With these I get a crank to piston deck at TDC of 211.2mm (8.31 inches).
I don´t know if your piston design could be ordered with this pin height.
Apart from that I´m only concerned with the really high rod ratio, 2.51. But it´s probably the best compromise in regards to reciprocicating mass.
Monday, September 16, 2013 11:49 PM
@josecabra, 1.14" should work ok. If you get the part from JE, you can reference job number 885110 and state your needed changes. You will need to have them decrease the valve relief diameters by 1 MM each back to stock. I'd take .025" out of the depths too. We had a ton of valve clearance. good luck.