Honda / Acura K20a K24a Engine Forum banner
981 - 1000 of 1026 Posts

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #981 ·
I don't think it's that biased... I'll have to ask. Just the rear axle assembly weighs 150 lbs, and that's without wheels and tires. When he hits a bump, it really hurts since the sprung-to-unsprung weight ratio is so bad at the rear. That said, he's a good driver and at the last Nevada hillclimb event, he beat everything except a 1200-hp GTR, and that included Ferraris, McLarens, and Porsches.

Says he needs more hp due to the altitude...
 

·
Arouse the DAMPFHAMMER!
Joined
·
8,024 Posts
...Says he needs more hp due to the altitude...
Thats the issue all NA engine driving hill climbers suffer from. Systems with an variability, like TC engines, can compensate a decreasing atmospheric pressure much longer as those who don't have such. The basic advantage is the so called load reserve, which is boost pressure after compressor and MAP. When bosst pressure decreases due to the decreasing atmospheric pressure (pressure ratio keeps constant, almost :D), MAP is kept constant as long as load reserve is positive. Designing the FI-concept right means same power under different atmosperic conditions, even it increases due to the fact, that the pressure drop over the engine gets bigger (= MAP - pressure before turbine or exhaust pipe pressure). Just once the load reserve get's negative, the FI'd engine system have big disadvantage, as MAP follows the factor of pressure ratio of the compressor = always bigger then 1. These means TC or SC design choice is competition-deciding. Walter Röhrl lost about 30 % of power during the Peaks Pike run from start to finish...something all hill climbers have to deal with. It could be also race-deciding, at which point of the race the load reserve zeros :wink:
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #983 · (Edited)
Don't visit here much since the password fiasco.

Anyway, took Midlana into Church for a "checkup" for several reasons.
- a lot has changed since my last visit (new engine, turbine housing, ECU, cam)
- My lingering concern that I or the previous tuner might have missed things
- The unknown reason why the first engine blew up.

So in went the car, a 2-hrs tow each way through LA traffic, ugh. Anyway, the obligatory video, https://www.youtube.com/watch?v=wLQVmW9NZZ4&t=5s

And here's a cut-and-paste from my blog:
30 Nov 2017


Get yourself a coffee – it’s a read.

I feel comfortable changing most engine ECU parameters, ones easy to monitor and correct, like idle, fuel maps, sensor calibration, and various safety features. On the other hand, cam and ignition timing scare me because there’s no easy way (on the street) to know what’s right and what’s too much. Images of holes in pistons from detonation, or valves hitting the pistons come to mind, so those were left as-set by the previous tuner. Reasons for the tune review include: never finding root cause of the engine failure two years ago, having changed cams and the turbo, adding a much larger intercooler and cooling ductwork, and a general insecurity that maybe I or the previous tuner overlooked something. Another thing that’s always puzzled me is how other people with nearly identical setups often report having about 20% more power with less boost. Given the high cost of rebuilding the engine, the peace of mind to have the tune checked seemed worth it. Church Automotive in Long Beach is about the best Honda tuner, and is also well-versed with the Infinity ECU, so I got to enjoy two-hour tows in both directions through Los Angeles’s finest traffic.

Once the tuning started, Daniel, the tuner, found that cam timing had been locked and asked why, given that it’s a fundamental reason why Honda K-series perform so well. I didn’t know and hadn’t touched it. He also found that ignition timing was off. The results of his changes were striking, finding 10-30% more torque between 2000-4000 rpm and 15-20% from 4000 on up. The improvement was enough that we mutually agreed to reduce boost to 15 psi, where it still produced 410 ft-lbs torque on 91 oct gas and 450 ft-lbs on E85. Horsepower was 475 on gas and 530 on E85. (With it as-is, it’s the same as running 1000-hp in a stock-weight Honda, given that Midlana is roughly half the weight). Even though DynaPacks and roller-type dyno readings differ by about 20% (which is nuts, but whatever), the fact that the car left with about 20% more power than it came in with, at lower boost, is what matters. The tuning session went almost flawlessly – except for one rather large event.

After completing a pull, the engine was shut down while various tuning changes were made, but then it wouldn’t start. At first I assumed that he’d “broken” the tune, but it eventually started, albeit with epic amounts of white smoke pouring out the tailpipe (I was too stunned to take pictures). Right then I thought I was looking at another engine rebuilt, but what didn’t fit was that it had completed the previous pull with zero problems – how did it break while sitting still? While it was running, we saw evidence of oil leaking around the turbo, so then I thought the turbo seal had failed, which was strange given that it probably only has 5000 miles on it from brand new.

The air filter was removed and there was oil on the compressor side, which meant the oil hadn’t originated from within the engine. Curiously, Daniel wasn’t concerned, saying that he’d seen this before on other cars and asked if I wanted to proceed. Not understanding what happened really made me want to say “no,” and if it was anyone but Daniel I would have, but given that he knows way more about Honda engines than just about anyone, I uncharacteristically agreed. He restarted it and sure enough, the smoke dissipated. We were able to successfully complete the remaining two hours of tuning without incident. So what the heck happened that it magically fixed itself? (I work in Field Support and things that magically fix themselves are always a mixed blessing.)

Oil coming from the turbo meant that it wasn't draining for some reason. The -12 drain line gravity-feeds into the pan, which is how virtually all turbo engines are set up. With this engine though, it also has a dry sump system, where scavenge pumps vacuum oil from the pan and return it to a remote tank. The combination of gravity-return and the vacuum should always insure all the oil returns to the tank, but for some reason it just wasn’t. Also, keep in mind that this exact setup has worked without issue for two years – so what changed? I have two theories, both involving the oil return hose:

Theory 1. The oil runs about 80-85 deg C (and the turbine housing, which is right next to it, gets way hotter). Both likely soften the rubber (steel-braided) return hose a little – or maybe a lot. Because the dry sump pulls a vacuum on the crankcase, could it have sucked the hose flat? Possibly related, all the other hoses on the inlet side of the dry sump pump have coiled springs inside to prevent collapse… but I didn’t think it through, that the oil return hose needs one as well, or it needs to be switched to a different type of material that isn’t as temperature sensitive.

Theory 2. Perhaps I inadvertently build the return hose with a “flap” in it (a known issue when constructing AN hoses, where the cutter on an AN-type end fitting can sometimes go into the hose slightly off-axis, resulting in it slicing off a slab of rubber hose material, which can potentially hang out in the oil flow. Maybe, combining the already-soft rubber and the vacuum allowed the flap to lift up and obstruct the hose? An inspection showed nothing, but with one end being a 45-deg fitting, I couldn’t see through it. A piece of welding wire was used to probe the hose assembly but failed to find anything. Still, one way or another, drain hose failure seems most likely given the evidence, so it was replaced with a Teflon hose assembly. I can see why people with big budgets use it; it’s noticeably lighter due to its smaller OD, even though the ID is the same. This should absolutely rule out the return line as cause and if it happens again, the turbo seal is then suspect, but how does such a thing magically fix itself?

One thing I don’t know is where the oil was burning. Smoke came out the tailpipe, but it could be burning in either the engine or the turbocharger turbine housing. One nagging thing is, what caused the engine to not start? (I forgot to ask if Daniel reloaded an earlier tune in order to get it to start, so maybe there were two separate things going on.) Anyway, knowing for a fact that the oil did come from the turbo is a relief (relatively speaking) so I think upgrading the drain hose is the best first step.

As an aside, with the engine running on the dyno, it gave a chance to see how well the intercooler ducting works. With a fan facing the intercooler duct, the inlet-side end tank was nearly too hot to touch, but the exit was practically room temperature.

Daniel said that this engine can reliably make 700 hp as-is, just turn the boost up – I can’t imagine. Shaun Church, the owner, said that they’d installed superchargers on Ariel Atoms, bumping power to around 500hp, but noted that their lap times typically increased due to them becoming a real handful. He also said that even over slight rises, they were lifting the front wheels off the ground, and asked if I plan to add a wing. Coincidently, my brother and I are currently considering just that.

I’ll work on the obligatory video next.
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #984 · (Edited)
And a follow-up post:
3 Dec 2017


Two steps forwards, one step back.

The tuning changes made a large and positive difference in power delivery. The tuner also changed the idle control, deceleration settings, and wall-wetting (compensation for fuel that ends up on the walls of the intake instead of the cylinders) along with many other things. Unfortunately I was itching to beat LA’s rush-hour traffic and declined his offer of a test drive… I should have done so. Now I get to do it myself via trial and error like before. I’m hoping I can reuse some settings from earlier tunes to save time – fingers crossed.

Before that was started though, the intercooler was removed, inspected, and cleaned. There was surprisingly little oil in it, with practically none at the outlet end and zero at the throttle plate. It “may” have been pushed through by the later dyno pulls, but it still raises two unpleasant questions:
1.Where did all the smoke come from?
2.Why didn’t the car start?

I think much of the oil likely flowed past the turbo seals (due to the theorized blocked drain line) and into the turbine housing. The housing was still hot from the previous pull, which reminds me of something. While it was smoking like crazy and yet not starting, as soon as he’d stop cranking the engine, about 2 seconds later, there’d be a soft “pop”, and an extra puff of smoke would come out the tailpipe. I’m guessing it was engine oil/gas lighting off in the hot turbine housing. This happened 3-4 times and always after he stopped cranking, so there was definitely oil pooled in the turbine housing, so, I think this part of the mystery is solved.

The second question is harder since oil in the turbine section shouldn’t affect whether the engine starts or not. The tuner confirmed that it eventually started on its own, he didn’t touch the tune. Problems that just go away… ugh.

Anyhow, the next thing to solve is how engine speed takes a nosedive when barely engaging the clutch (like leaving from a standstill). It may well be insufficient wall-wetting. We’ll see.

In other news – don’t remember if I mentioned it – earlier this year my brother got fed up with his GoPro, replacing it with a Sony action-cam. He can’t say enough good things about it, and it’s mostly because the Sony, well, it just works – every time. I’m sympathetic; my GoPro 4 (with the latest firmware) still had demon-possessed moments. Starting a second video by itself, resetting itself, and my favorite, acting exactly as if it’s bricked, then works days later like nothing was ever wrong. I have to give GoPro’s Marketing Dept props for still selling even with pissed-off owners. Point being, if you’re looking for an action cam, consider the Sony.
 

·
Arouse the DAMPFHAMMER!
Joined
·
8,024 Posts
And a follow-up post:
kb58, an increased MAP would consequently cause a higher pressure drop over the compressor, increasing the blowby rate over its oil labyrinth sealing. There are a certain level of pressure difference where the blowby flow increases non-linear...especially once the sealing has some sign of wear.

The poff effect you described is likely a phenomen called flash fire in the exhaust runners, a deflagaration flame type, caused by misfire in the combustion chamber, so that fuel and air is collected into the exhaust manifold and get's ignited after ignition parameters exceed autoignition conditions. In such a flash fire, it could be oil get transported over the sealing system into the intake (post compressor side).

TC'd engine systems have a systematically higher likelyness to misfire at idle conditions due to the higher backpressure at exhaust side, the lower CR (both increases residual gas content at ignition timing). Did you check your spark plugs before there is a need to dive in more deep?

To the nosedive (nice word :D) of the engine speed, I would agree with you, leaning at tip in is often a cause of transient torque dip. You likely can't see it at the wideband, just in the delayed sensor signal reaction of it (t90 time of it is too big) and mainly in the engine speed signal...within a TC system the tip is is a pitty to tune, as disturbances, e.g. like the delayed speed increase of the compressor, add additional oscillations into the loop control of fuel mixture. As an software engineer you likely know that even better. You here that on race cars, getting out of the corner, when their engine noise oscillates slightly over the engine speed increase...it is always a fight of several forces, torque systems against the aimed change in engine speed.

I would check spark plugs and the secondary circuit of the ignition system first before any action.

Markus
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #986 ·
You're right, I should at least check the plugs and will do so.

The smoke never happened before that day and hasn't happened since. The MAP has actually been decreased, from around 19 to 15 psi. The only significant changes are cam and ignition timing. Well, that, and replacing the turbo oil drain line. I realize changing more than one thing at a time can make finding root cause difficult or impossible. For now, idle tuning and test drives continue, but so far so good.
 

·
Registered
Joined
·
115 Posts
In my opinion, you should not exceed 400whp, with this power you can not control the vehicle. I have a 485whp turbo engine in L7. After a few racing seasons I think that the power should not exceed 300whp as in R500. Because it can be very dangerous.
That's why I mount k20. N/A
 

·
Arouse the DAMPFHAMMER!
Joined
·
8,024 Posts
In my opinion, you should not exceed 400whp, with this power you can not control the vehicle. I have a 485whp turbo engine in L7. After a few racing seasons I think that the power should not exceed 300whp as in R500. Because it can be very dangerous.
That's why I mount k20. N/A
Hi Adam, I agree with you. I personally also don't like to drive a 500+ Nm engine in an 700- kg chassis as you can spin all the time up to 4th gear at least, especially if power increase happens after TC lack is overcome. Driving it with slicks makes it even more challenging due to the smaller no-spin-now spin-bandwidth.

Driving on the limit of the engine on a much more easy to control engine power curve and response is much more fun as mostly the drivers talent dictates you the lap time (s. FSAE, Formula 3 and 2, Group H and lower of DSMB, ...). In a more less linear and much more lifted power curve a lot more comes into play, engine response get's an huge factor, TB to load linearity and sensitivity, slip control, torque control for gear safety (E-engines especially :D). These are cost runners and of course brings driver more often at his limits if no torque, slip, brake, aerodynamic, ...system supports the driver.

So one could say, hey this is a training machine for the driver, challenging his skills all the time. Other ones like you say, it is dangerous to drive it and recommend a calmed version of it. I will quote one of the best Ralley car racers ever, Walter Röhl, who rode the legendary AUDI S1, who said, the B-series World Ralley Class cars (around 500-560 whp) are monsters, which need extraordinary driving skills, to such an extend, the driver have to feel what to do next even before he can see e.g. the corner. To get an impression of Group B WRC of the 80's, the most deadliest, challenging and most brave demanding racing series ever.


So I totally agree with you, but I believe the US guys have a different unterstanding of car driving, they have much less corners in streets, they have regidious speed limits on streets and on the tracks many of them just have fun to see what the car do on straights. Here in Europe we have challenging conditions by cornered streets, high speed ways without speed limit and we have the most challenging tracks here and to drive here is understood to squeeze out everything you can...so I am impressed you where able to challenge with others so long with your TC'd Lotus Seven. I you will have NA wise a bit more fun and see your car from a other side.

Onboard impressions of the Group B WRC

Pikes Peak

The Röhl-Genius at work :D
 

·
Registered
Joined
·
115 Posts
I haeve two L7. One with motorcycle engine 185hp with total weight 485kg and second one with car turbo engine 485hp with 560kg.

Which one is nicer to drive and faster on the track?
:blur:
first one. but there is no power from 200km/h
So I think the ideal will be 270hp and 500kg. Just like R500.

Regarding Walther, many drivers from that period also spoke so beautifully about group B. But not many survived. Which does not change the fact that the B group drivers were not normal;)
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #990 · (Edited)
In my opinion, you should not exceed 400whp, with this power you can not control the vehicle. I have a 485whp turbo engine in L7. After a few racing seasons I think that the power should not exceed 300whp as in R500. Because it can be very dangerous.
That's why I mount k20. N/A
It's not that simple because it's subjective and specific to the conditions. First off, who's using 300, 400, or 500 hp in the turns? Here, we have large tracks with long straightaways. Autoclub speedway, a NASCAR track, is an oval where many trackday cars run >150 mph down the front straight. With a car as draggy as a Seven, I need power to keep up with far more aerodynamic cars. My brother's LS3-powered Seven is running 160 mph down that straight and has 430 hp, but I'll let him know he needs to turn that down to 300. Yes, running that much power in such a light car is dangerous, yet come to a hairpin turn in a car running 100 hp without lifting and that's dangerous too, but not due to the power at-hand. In a straight, being able to pull a Porsche GT3 requires power to overcome drag.

On the street it's run with perhaps 300 hp, so I meet your requirement. It was mentioned above that wheelspin becomes an issue at those power levels. Again, it depends upon things such as aerodynamics, gear ratios, tires, tread compound, and importantly, load. Being mid-engine, I can put down 400+hp way better than any FWD due to having more load on the driven wheels. Traction in second is iffy, but third and up is no problem. Speaking of load, we're currently looking into adding wings to our cars, does this change the 300 hp magic number? Since wings increase drag, it'll slow the car down, but your 300-hp limit doesn't allow taking that into account.
 

·
Registered
Joined
·
115 Posts
If you drive on NASCAR tracks, I agree 100%.

And this is how our Sunday competition looks like. It`s 185hp
https://www.youtube.com/watch?v=v6N3BKEH8a0&t=

We do not run on NASCAR tracks because we do not have them :) We ride in a natural Lotus 7 environment.

But I agree, in my 485 at speeds above 300km / h the front begins to rise dangerously.

And in the corners only mass counts, and you can not fool physics.

But it's great that I met another person who knows that only the engine is suitable for racing with HONDA.
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #992 ·
... Traction in second is iffy, but third and up is no problem...
I'm now wrong on this but in a good way. The last dyno session found 10-30% more torque just about everywhere and I finally turned up the boost briefly and got on it in second gear. Yup, it's no longer "iffy" and is now firmly into "wheelspin." Since the car's running a PPG 1.66 second gear, a 4.374 rear, and ~25" tires, second is good for something like 80 mph. Haven't tried it in third due to not having the runoff space.
 

·
Premium Member
Joined
·
10,576 Posts
Curious on actual size and wonder if a stickier compound in the current size would help. Either way instant wheel spin is always 'invigorating'
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #994 · (Edited)
Toyo RA1. Fronts are 205(?) 17s and rears are 275 17s. Treadwear is 100 or so, so very sticky. That said, they're 7 yrs old and the rears are in need of replacement. They'll be replaced with Nitto NT-01s.
 

·
Premium Member
Quantum GP700
Joined
·
771 Posts
Going wider with the rear tyres might not work as the grip is tyre temperature related as well as the contact patch.
Even with TC I had safety issues as my car would step out on flat shifts, and cut cylinders during acceleration to find traction. So my solution was to map the available torque with my Quantum GP700. The driver controls a cable throttle on the manifold. The bravery pedal. A second throttle before the SC is DBW and computer controlled. This is multi D mapped rpm V (gear, road speed, lateral G, vertical G and a driver trim knob). As it's supercharged boost is always the same for a given rpm so the torque result is really predictable and this mapping really works well as it controls the maximum boost the driver has available.

On a high speed straight we have 100%, on a shift the power ramps in over 0.25 S. In a corner it might be reduced to 30% depending on speed, gear, etc.

So in corners you can be aggressive without fearing the power.

Acceleration is 1.3G with 295 rears, 1.15G with 265. The only tyres I have found that work are Yok A050's or Dunlop DZ03G both in soft compounds and you still need to warm them up before getting too excited.

This power to weight is really addictive and I love it!:devil:
 

·
Arouse the DAMPFHAMMER!
Joined
·
8,024 Posts
Toyo RA1. Fronts are 205(?) 17s and rears are 275 17s.
For my NA engine I have 205/45R16 at the front wheels and 235/40R17 at the rear wheel. Tire is Kumho Ecsta V70A (medium)...pretty good for dry conditions and slalom, hill climb, but tricky at wet conditions...of course no real traction issue with an 3 kg/hp car...LOL :D.
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #998 · (Edited)
From my blog:

I'm considering having another transmission built. Since completing the car, there's been plenty of time to evaluate the current transmission, a modified DC5 transmission with straight-cut aftermarket gears for 1-4, OEM 5-6, and a WaveTrac limited slip differential.

For the street the transmission's perfect, but for the track, the gearing isn't optimum because the engine's turbocharged. 5th and 6th, being OEM, are designed to handle ~160 ft-lbs and not the 400+ of a turbo engine. I take it easy in 5th and 6th which is probably why I haven't broken them like other people have with their 500+ hp.

Since the existing transmission works great, I'm considering selling it and using the money to offset the build of a slightly different version, starting with an RSX-S 6-speed, but with:

1. Full aftermarket 1-6 gears with lower ratios, and stronger 5th and 6th
2. OS Giken LSD (one-way)
3. Carbon synchros

Reasoning:
I want ratios better suited for trackday events (numerically lower) and talked to Jaydee who assured me that while many people claim they're terrible, he pointed out though that our enormous advantage is how our cars weigh literally half what everyone else drives, so the car has no problem leaving a stop in first gear (2.313) with the stock 4.38 final drive ratio.

The differential is being changed to an OS Giken LSD, said to be good for several seconds a lap due to how it locks up. It's also supposedly easier to control the attitude of the car in turns. Both of these feature are very attractive. BTW, I had a long discussion with Giken US and for my mid-engine car they recommended a "reverse 1.5 way" configuration.

I'm going back to helical gears simply due to cost and availability, and because the helical set claims to be able to handle 500 hp. Additionally, the carbon synchros should prevent the dreaded Honda 2nd-gear grind due to them wearing prematurely.

Haven't decided for sure but I'm close, and am currently waiting for some answers about whether the OEM final drive is safe to leave in-place.

Okay, okay, there might be one more perk of the above gear ratios. Between the new first gear ratio, the existing final drive, tire diameter, and my engine's red-line, I would be able to reach 60 mph in first gear - something I've always wanted in a car. The reality is that it's totally pointless and only good for setting a rather awesome 0-60 time :)

Lastly, with an unlimited budget I'd love to try a sequential gearbox but can't justify the ~$10,000 entry fee, plus having it become a wear item that requires periodic teardowns.
 

·
Arouse the DAMPFHAMMER!
Joined
·
8,024 Posts
...I want ratios better suited for trackday events (numerically lower) and talked to Jaydee who assured me that while many people claim they're terrible, he pointed out though that our enormous advantage is how our cars weigh literally half what everyone else drives, so the car has no problem leaving a stop in first gear (2.313) with the stock 4.38 final drive ratio.
I definitely would also keep the door open for different and specific solutions. Therefore I developed my dynamic chassis model (DCM), where track data can be feed in and the DCM will answer what the car is doing with its torque. I believe Jaydee has something more simplificated (straight acceleration) shown in the PPG-thread. Once you know your slip torque and slip torque gradient it is a powerful tool not only to optimize your 1/4-mile times.Your power-to-weight-ratio need definitely an individual and specified gear set to get it handled on track. This also depends on the engine setup (transiend torque build up) and your prefered driving style (understeered, oversteered, neutral). A clearer picture could be illuminated in the log data by comparing e.g. gearforce vs TPS and VSS vs tire speed.

What are the options you are considering or which are available kb58?
 

·
Registered
Joined
·
2,807 Posts
Discussion Starter · #1,000 · (Edited)
My car project is just for fun; I don't pretend I'll ever be a pro driver and don't compete in anything that has any reward other than just being there. So while I completely agree with you, I don't have the drive or need to calculate the exact right ratios. That said, I can also understand someone saying "If you're going to spend the money, why not spend it on the correct ratios instead of some random (and likely wrong) set?" Fair point.

I've done a lot of research regarding what's used in similar cars and have spreadsheets to find the rpm drops between gears and the expected top speeds, versus the torque and power curves of my engine. For example, Gear-X has two sets that differ only in 5th and 6th. One allows a top speed of 170 while the other is 162. I know from experience that my car's unlikely go faster than 162, plus, this speed estimate is "pre wing"; once they're added, the top speed will very likely drop well into the 150's, so I'm leaning toward the set best optimized for that expected speed.
 
981 - 1000 of 1026 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top