SK400

Micheal Avon states 22" diameter for my size of rear ZZR tires.. (if that's your question). I'm really revving, probably around 7600 to 7700 RPM to get those speeds. Which is a lot for this engine... Tail wind might have helped a bit that day.

I finally had the chance to try the car for the first time on a track this season last weekend. I joined my good friends at NJMP for a fun HPDE event and was able to compare and contrast this year's performance with that of last year, before installing the throttle bodies and bigger injectors. I did have a fresh set of tires which counts for a lot but with this in mind, I was able to shave about 1.5s per lap without any particularly refined / consistent driving and with some traffic on the track. The big noticeable differences were (a) top speed, where I used to max out at 127 - 128 mph and now reaching 134 - 135 mph at the end of the NJMP lightning straight, (b) gear change timing especially from 5 to 6 coming out of turn 5 and 8 (the bowl) and © the sound! I can finally hear my car over the exhaustless miatas and porsche caymans who can pierce your ear drums a mile away.. So overall - a good upgrade I would say and would encourage anyone not subject to track decibel limitations to consider this throttle body upgrade for their R300 - R400... the car comes alive.

Really??!? Were you intentionally trying to wear the tires out? I know the bowl is unforgiving for front tires ... but geesu. I hope at least, for the time it lasted, you enjoyed a bit better traction and handling with the A24. If not, well i'll be in big doodoo with tire budget for the year.

Not so fast Mike (clearly, you know how to press on my buttons). Just got myself a fresh set of ZZR tires with a24 compound this time. (I just leaned that I've been driving on the harder a64 compound for the last 2 years). So bring it on! All good fun

Well here is the moment of truth folks! I took the car to a Dyno at P1 Motocars in Stamford, CT, for a few pulls. This is a top of the line shop and highly recommended if you want to have some work done on the car and in the region. (engine, alignment, general maintenance, mods etc). Here it is: a) Without R500 airbox cover: 198.42 HP @ 7250 RPM and 158.4 ft-lb @ 6100 RPM at the wheels on the graph, although in the shop, we had read a very consistent 199.5 HP on two separate runs (probably with a different correction value). Shall we call it 200 HP at the wheels? Applying a 10% transmission loss factor (a reasonable estimate for this simple drivetrain, but you tell me) to the 198.42 HP, this translates exactly to 220 HP at the flywheel, which is what Caterham had advertised with the throttle body upgrade kit. I unfortunately do not have a Dyno reading for the original R400 setup but literature puts it at 210 hp @ 7600 rpm and roughly 149 ft-lb at 6300 rpm. I think the 210 HP was right but doubt the 7600 RPM as I know the car struggled past 7500 RPM and hit the cutoff around 7600 / 7700 RPM or so in the past. So net net, a good 9 to 10 ft-lb increase probably really above 4500 RPM, a 10 HP top end increase as a result and a lot more sound, (a lot). Note that this test was conducted using regular 93 octane gas and had noticed significant difference in the past when I used 93 octane from race tracks pump. Also important, I have ZZR tires and pressure was set to 18 psi.. as a few psi more could have changed the readings slightly. Temperature was a comfortable 68 deg and 50% or so humidity. b) With the R500 airbox cover: 192.4 HP at the wheels and 154.4 ft-lb so about a 6 HP and 4 ft-lb of torque drop from the filter only version. Applying a 10% transmission loss correction factor to the 192.4 translates to 214 HP at the flywheel. So this cover saps a lot of power unfortunately and only helps a bit on sound. But it looks good J . The graph below represents with and without the R500 airbox cover. The blue line is without and the red line with. In conclusion, I think the upgrade was worth it but will really pay off on tracks where I’ll be able to run without the R500 airbox cover (example NJMP), where decibels are not an issue. I live close to limerock and normally enjoy a clandestine track day or two there during the year .. but I fear that now, even with the cover in place, I might get myself into decibel trouble for very little horsepower increase (4 HP), not enough to make a difference on lap times. But I’ll see. I’m eying a session on May 22nd and will give it a try. Since the car is now already loud, I may just decide to go full out, and complete the engine upgrade , shooting for a 270 HP setup with the help of the UK tuner SBD. See you soon on a track! Seb http://www.usa7s.net/vb/attachment.php?attachmentid=12601&stc=1http://www.usa7s.net/vb/attachment.php?attachmentid=12602&stc=1http://www.usa7s.net/vb/attachment.php?attachmentid=12603&stc=1

Bruce would you mind attaching a few pictures of both? thanks!

Slight correction - P1 Motorcars

P1 Motorsports in Stamford, CT. A good shop. Candidly, I wont be tuning much on the dyno simply because my ECU is locked by Caterham. But they also have great alignment equipment, scales etc and last time I went in for suspension and alignment tuning, the owner did all the work himself on my car.

Simon, good to hear from you. Let's see if this upgrade really helps with lap times.. I suspect that it will still be really difficult to follow you and keep up with your pace!! On a separate note, I have a dyno test and tune appointment on May 6. I unfortunately don't have the pre-readings but still curious to see what the engine puts out with the roller barrels. I'll test with and without the R500 carbon airbox.

Friends What is the tally right now? I'm counting the days ... Can't wait to see you all soon. Blake, will we see you with your car? Will you have completed it in time?

What a great day on the east coast. Could not resist to take the car out for a spin. Overall, i like the new engine setup, but it feels like it lost a bit of low end torque (under 3000 rpm) or not as responsive off the line .. but then it corrects the the car feels solid and stringer especially above 4500 rpm. I still plan to dyno the car soon, but has anyone experienced a change in torque (lower?) under 3000 rpm when changing to roller barrels, especially when opening the rollers suddenly? just curious.. thanks!

Alright! I finally received the ECU back from the UK, completed a few checks, and finally took her for a spin today. OMG.. felt strong, perhaps more torque than previously but probably the biggest difference is the sound! unreal.. roller barrels with cat bypass changed the RPM tune completely. Pretty decent and "civil" at 3000 RPM but past 5000 RPM, it is a screamer. Plus lots of backfire when I let go of the pedal rapidly. My only concern right now is if i'll be allowed at LimeRock ( able to meet the decibels rules?). I have the r500 carbon fiber airbox which helps... but i guess we will see. Next will be to dyno the car to see what this upgrade really did. Will keep you posted.

I now have the ZZR 185/55/13 in front and 215/55/13 in the rear, on caterham apollo rims 13x6,5 and 13x8.5 i think. Looking for a bit more tire in front potentially. And yes, i do have a dry sump, so we are all good for north of 70 - 75 mph in the bowl.

Agree! Just missing my ECU stuck somewhere between the UK and the US. Probably victim of the new travel ban as well. Hope to receive it before July 1st but i may have to apply for special ECU visa. As an aside, looking for used set of 13" r500 or BBS rims for slicks. Determined to get in the low 1:12 or mid 1:11 s at lightning. Any idea? Lastly, Blake, any chance you ll be ready with your car by then? if you work day and night, could be a great milestone for you.. Would be fun to drive together - caravan style - from CT.

Friends, After a nice 2 days with family skiing in Vermont, I took a few hrs late Monday night to complete, mostly, the throttle assembly. I say mostly because there are still a few things to iron out including re(re)flashing the ECU. Here are a few tips for those attempting to install the kit. 1/ Installation of the Carbon Airbox and pressure sensor: when I installed the pressure sensor on the carbon airbox, I used a bit of RTV to ensure a good seal between the sensor and the surface of the airbox. There was a very thin opening between the airbox sensor hole and the back of the sensor body that needed to be sealed. What’s more, I layered a very thin layer of RTV on the front machined surface of the throttle bodies to ensure a good seal with the airbox and avoid any leaks. Lastly, I made sure that the carbon aribox air openings (the holes) did not obstruct, even partly, air flow when installing the box. I had to shave off a bit of the diameter with sand paper. 2/ TP sensor: I started the engine and with the alternator powering the system, recalibrated the TP sensor to 4.62V for an idle opening of 6 mm. There was indeed a small 0.05v or so difference when calibrating the TP sensor using the battery only versus when the engine was running. The voltage output went up with the alternator running. 3/ Tachometer: now that the engine was running (nice throaty sound ), I noticed that the tachometer did not move much as I was revving the engine up. It showed about a 4th of what it should indicate. Discussing with Mark Rider from Caterham (very very helpful BTW), we realized that the ECU needed to be reflashed for separate coils configuration (need to pick up 4 pulses versus 1). So I ll have to send the ECU back to the UK. No biggie.. Here’s the finished product with and without the full race carbon cover. The opening is a bit big for the foam filter only but not as bad as I thought it would be. Looks awesome and perfectly matched for the Carbon Cover though. Quite happy with the finish and look. Can’t wait to drive the car this spring and “feel” the difference. Oh yes, still have to install the cat bypass which should help for sound as well. http://www.usa7s.net/vb/attachment.php?attachmentid=12263&stc=1 http://www.usa7s.net/vb/attachment.php?attachmentid=12264&stc=1 http://www.usa7s.net/vb/attachment.php?attachmentid=12265&stc=1 http://www.usa7s.net/vb/attachment.php?attachmentid=12266&stc=1

Yes. mostly through throttle.. feathering in helps a ton.

I have the ZZR 185/55R-13 and 255/55R-13 setup on my 210 HP R400 and it works well although you may have to get a bit of toe-out to increase front end corner entry grip or stiffen very slightly the rear sway bar to get the car turning when really pushing it. With this setup, and tire selection, you should be in very good shape.

LOL! I agree. I really wanted to go to Mars with that degree but obviously this did not pan out..... I guess it will be for another life. But not before I finally learn how to install a set of throttle bodies with no drama, in this life or next.

Hooray! The engine started without hesitations ! I guess i got lucky. Here are my lessons learned on this step for those who will attempt this on your own: 1/ Setting the TPS sensor: after setting the throttle body openings to 6 mm using the shaft of a 6 mm drill bit and playing with the idle and throttle balance setscrews to get there, I rotated carefully the TPS sensor until the voltage read 4.62V on the nose. Please note that you should a) ensure that you have a fully charged battery (if not it will give you false readings) b) turn the car on (but not the engine of course), and use a multi-meter, inserting the probes into the back of the TPS connector and take the voltage between ground and middle sensor wire. Have the TPS sensor screws snug to allow rotation but not too much play. Once set, remove one TPS sensor screw at a time and add some blue loctite to the threads just in case and rescrew. Repeat for the other screw. When complete recheck the idle TPS voltage and ensure that it still reads 4.62V. -(still need to check TPS voltage when engine is running... wondering if it changes because input voltage may change a bit as the alternator helps the battery - actually this is a question for the pros, Bruce, others, any advice on this later point?) 2/ engine belt tensioner bolt clearance: I took my time but with the help of a large 9/16 drill, a dremmel tool, files and sand paper, i manage to counterbore nicely the casting and removed about 1/2 inch (a bit less) in length. I bought a new M8x1.25 bolt at the local hardware store with about 1/2" less in length than the original bolt.. et voila. It creates enough clearance for the carbon airbox the be installed. See below the voltage of the TPS sensor at idle. Also a short video of the engine running. Idle RPMs were pretty low (500- 600 ROM ish) - but perhaps it is because the temperature was cold (32 degrees in the unheated garage). I may have to simply adjust the idle this spring after taking the car for a little ride and with the air filter etc installed. Next step is to install the carbon airbox, air trumpets, filter etc. and see it completely assembled. cheers to all http://www.usa7s.net/vb/attachment.php?attachmentid=12201&stc=1 http://www.usa7s.net/vb/attachment.php?attachmentid=12202&stc=1

Tom I thought you you were going to say " KitKat is really just an obstacle on the track otherwise" .. but i guess you were kind with him this time around..

Ditto. Gorgeous. I hope your car is wrapped with 3M film or equivalent (and I mean the whole thing wrapped). Would hate to have you drive behind Kitkat this summer and have you and your car age 1 yr per lap because of all the rocks he throws back at you. Just something he does to all of us.

Slowly making progress in the assembly. Last weekend, I spent some time adjusting the idle opening of the barrels to make sure that the right and left hand sides were set to 6 mm opening. I also got very lucky.. i snatched a rare R500 Carbon Airbox directly from Caterham which acts as a cover for the sausage filter and fills the opening i had cut in the bonnet beautifully. I'm really happy about this (looks great.. as good as factory). I hope to dyno the car this spring and try with and without the cover to understand the difference in performance. I also think that the cover will help me be "sound legal" at LimeRock, which is a good thing. I'm not yet done with the belt tensioner modification. Looking for the right fastener (may have to look at McMaster Carr as suggested Dave) before modifying of course. That said, i think i can at least try to start the engine. I received my ECU reflsahed from Caterham. I will have to set my TPS sensor.. and then.. turn the key. Suspense.. Will let you know.

Nice! love the list building up. Welcoming a 620R to the track and event will be fantastic. Can't wait to see everyone again soon.

Same here. My wife drives a 1275 '78 mini in the summer. Two days in a row, bought the Caterham and Mini shirts for the whole family including my two kids. Tapped out of Blipshift budget this month.

Super helpful Mike. thanks a ton for the links. Where the folks at Caterham talking you down from installing the race air box? or the track day one?