This article covers the Bell Engineering Group Inc (BEGI) NSX twin turbo kit equipped with Aerocharger turbos and Cartech- branded kits equipped with conventional turbos. If more information about the Cartech kit will be added, a new article should probably be created (and cross-linked to/from this article).
Corky Bell founded Cartech in 1977. In 1992, he formed Bell Engineering Group Inc (BEGI) and developed the Aerocharger equipped TT kit. He stopped making the TT kit when Aerodyne (makers of the Aerocharger) looked to be going out of business in 2002. For several years, there was no support or servicing from Aerodyne so the market for the BEGI TT kit understandably dried up.
A couple of guys stepped in and bought the rights to the kit, including the name of the company, Cartech, and set about converting the turbos from Aerochargers to T28 conventional turbos, which required an oiling system. They apparently had a poorly designed oiling system and even worse customer service (ask Jorligan), so they quickly got a bad reputation for their kit and perhaps ruined the reputation of the original Bell TT kit by association. Cartech’s new owner’s adaptation lost two of the best qualities of the Aerochargers, self-contained oiling and variable vane turbine nozzles.
The original Bell TT kit got good reviews before the Cartech successor episode. Seemingly, the only complaint back then was the fuel/ignition system (which had basically the same plan of attack that the CTSC used) wasn’t reliable enough.
Current Vendor Info
- Web Site: http://www.bellengineering.net/
- No NSX kit listed on web site.
- Web Site: http://www.aerocharger.com/
- The owner, Brad Riley , has recently (August 2010) confirmed that they do service/support the turbos used in the original Bell/BEGI kit. In addition to repair work and selling new units they offer a preventative refurbish service (tear down, clean, balance, replace consumables) for $179 per unit for those interested in that piece of mind.
- Web Site: http://www.cartech.net/nsxturbo.htm
- Above link goes straight to NSX kit info.
Technical Details – Bell/BEGI Kit
There were two sizes of Aerocharger turbos used for these kits. More info (specs, model numbers) on them would be good.
Technical Details – Cartech Kit
Place info not on vendor web site here.
- Bell/BEGI marketing packet for NSX kit: PDF
- 1993 article on Bell/BEGI NSX kit in “Turbo & Hi-Tech Performance” magazine: PDF
Original NSX Prime FAQ Entry
Bell’s NSX Twin Turbo Kit
|Bell’s published performance data:|
|Stock||BEGI Twin Turbo|
|Power (crank HP)||270||390|
|1/4 mile time (seconds)||14.4||12.8|
|1/4 mile velocity (MPH)||99||113|
[BB] My car’s measurements at the wheels: (Running 5.95 PSI): 334 hp @ 7800 RPM (which was calculated by the shop to be 412 crank hp) and 280 ft/lb torque @ 5800 RPM (which was calculated by the shop to be 348 crank torque)
The dyno of a ’91 NSX from Mech-Tech shows: 328.4 HP @7000 and 272.3 ft/lb torque @ 5200 RPM. They did not extrapolate for crank HP. The car was running 5.5 PSI. They also listed stock numbers for the car they dynoed prior to installation of turbos and fuel system upgrade: 223.6 HP @ 7800 RPM and 176.8 ft/lb torque @ 5500 RPM.
I did not have my car dynoed before installation, so I don’t have a control for comparison
[RF] My Bell Twin Turbo (and other than that stock) ’92 NSX with 16,500 miles, has a recorded run of 12.668 in the quarter @ 113.3 mph.
For upgraded fuel delivery systems required to safely use the TT kit, there are two companies you can use – Toyomoto in Miami (305) 378-9325 speak to Lance Holung and Mech Tech in CA (619) 432-0555 and speak to Jim Macfarland.
[PD] I have had one on my NSX for 2 1/2 years now without a single hick-up. It awesome and an absolute thrill to drive each and every time I get in the car – which is just about everyday.
[RF] I concur with Paul, I have had the TT for a year, no problems and it is exillerating. 12.6 quarter mile. All stock except the TT. I have a 92 with 16K.
[AE – 99/7/26] My own experience with turbos has been nothing but good.
I have had BEGI turbos on my ’91 NSX for about a year and a half, during which I have put about 6000 miles on the car. The car is very powerful, smooth and drivable, and so far has not missed a beat. My driving style is relaxed, with occasional bursts of pedal to the metal for a few seconds. I never stay on full throttle for more than 15 seconds, and have not yet exceeded about 155 mph. I don’t race the car, but like powerful acceleration. (The car has the 4.55 r&p as well.)
Avoiding detonation is, I believe, the critical factor in keeping the engine in good shape. Careful installation and set-up are the key to success. (Set max boost to 5.5 psi, for about 90 more horses at the crank!) To be extra careful, I use 94 octane Sunoco fuel. I once wrote a report about the process of putting turbos on my car. Anyone contemplating doing the same may want to read it for tips on performance, set-up and how to make it look clean. Private me if interested.
[BB] To provide enough fuel for the turbo cars (BEGI) at any boost over 4 psi, just increasing the fuel pressure is insufficient (can you say "Eric Kerub"?) as the stock injectors are not capable of increasing the fuel demands required.
Your options are to utilize a computer management system that can accomodate larger injectors, (based on air densities [MSAC], or RPM dependent with adjustable parameters depending on the application [vein-pressure controllers] or
(like what Mechtech has done, and I run on my car) use an additional injector controller that will operate 2, in my case, additional 360 cc injectors providing adequate fuel for 6 psi. Actually, our stock fuel pumps are adequate even for additional injector application--it is important to change the fuel voltage to a continuous 12v supply, as stock it runs at 6 or 9 volts (I don't remember) until 5500 RPM, at which point it switches over to 12 volts. Without the switch, you will run lean below 5500, as the stock pump will not provide enough fuel.
The additional injector controller is nice in that as long as you are not under boost, your car is not running rich, so your fuel mileage is essentially unchanged from stock, though YMMV depending on the use of your right foot.
Bell Twin Turbo Horror Story
[EBK] PART I (Originally written mid-April of 1997)
Well, here’s the story.
Although I was very pleased with my Turbo kit, I realize now that I was like an emotional kid when typing my original reflections. A lot has happened since that post. Some of you are aware (Richard, Ben, Andy, etc.) and I would like to thank you guys for lending me an ear during this quite depressing stage of my life. For those of you who don’t know what happened here is the WHOLE story!
I received the kit on Friday afternoon April 4, 1997. Took it home and started unwrapping. My friend/mechanic and I started looking at all the parts and categorizing them on the floor. The first thing that wasn’t too professional was little bits of Styrofoam in everything. The exhaust tubes, intercoolers, inlet and discharge tubes….everywhere! They definitely needed to be air gunned out.
***Time-Out*** you won’t believe it….Corkey just called as I was writing this! I will get to our conversation at the end of the story.
Anyway, The next morning we woke up bright and early and started working on the car. After removing the stock parts, we started going through the kit and reading the instructions. As mentioned before, the instructions were a mess. Furthermore, many things were incorrect with the kit. Imagine trying to read a *bad* set of instructions and figuring out what part goes where when the part isn’t even there!!!
Below are some of the headache’s I’m talking about;
- The signal block solenoid had no vacuum hose fitting
- The hub switch was set at 0 vacuum
- Vacuum hose for the turbo gauge was too short
- No fittings were installed on the intercooler discharge tubes
- There were no provisions to install the breather hose for the inlet tube.
- Aux. Fuel pump inlet was way too big to fit original fuel hose
- No installation instructions for the aux. Fuel pump whatsoever
- We suspect that the fuel pressure regulator was never tested because all components were loose and not adjusted.
- Installation refers to a "label #2" on the solenoid for a vacuum hose installation…no label #2 on solenoid.
- Instructions say to install the by-pass valve to the right turbo unit. It must be installed on the left unit.
- Emergency control valve inlet was too small to fit the EL adapter
- Instructions say "The vacuum signals will attach to the fittings on the big end of the actuators. Two lines must be run from tees placed in vacuum lines at the main sensor box." Which vacuum line???? If you use the #4 line as we did, it will mess with the map sensor and intermittently cut the engine under boost!
These were some of the problems encountered worth mentioning. Others were a collection of small annoyances which took visits to the local hardware shop to purchase items to fabricate our own parts.
We waited till Monday to call Corkey about that intermittent engine cut off (the #4 vacuum line) and finally got the car working properly…or so it seemed. We went for a test drive with the fuel pressure gauge taped to the windshield and the turbo boost gauge in the glove box to measure the readings under boost as per the instructions.
The instructions say:
Fuel pressure must function as follows:
|50/55 PSI||1 PSI|
|70/75 PSI||3 PSI|
|80/90 PSI||5 PSI|
The problem with this is that 80/90 PSI of fuel is not nearly enough to run 5 psi of boost on the NSX. We were hearing mild pinging at high RPM in higher gears (3rd & 4th ). We mentioned this to Corkey and he told us to get the fuel pressure as high as 105 PSI. The problem that occurred was that the fuel pressure regulator was already maxed-out.
Under full throttle the needle would instantly peak at 90 PSI but then start dropping down to 80 PSI and maybe even lower (the needle shakes a bit while driving). From Monday to Friday we were constantly trying to get more fuel in the car under boost. Michael, my mechanic, was on the phone every day talking to Corkey. Corkey kept telling him to try "this and that" to get the fuel up.
Finally by Friday I set up a conference call with Corkey, Michael and myself (I was at the office). Michael explained to Corkey that he had tried everything, and still not enough fuel was getting in. Corkey mentioned that he was building a new batch of regulators and he could send a unit up for us, but he wanted us to keep trying different things on the regulator.
Being the nice guy that I am, I told Corkey that he could hold off on sending the unit up until we tried the last few suggestions he made over the phone. Michael had no objections and proceeded to do what Corkey asked him to do. Two hours later I get a phone call at work from Michael; "BAD news…blown engine!!!"
"What the.." I responded, and asked what happened. Michael had gone out on a road test with my girlfriend (so that she could monitor the boost, while he monitored the fuel) and the fuel pressure went from 90 PSI to 70 PSI instantly, and under full boost. By the time it took to react and let go of the throttle (.5 sec maybe) the damage was done.
I came home early from work and talked to Michael a bit on what happened. For those of you who are reading this and do not know me or Michael I must make something perfectly clear. If Michael had caused the blown engine in any way shape or form, he would have been the first to own up. I’ve know him for almost 7 years and he is a friend of the family.
As far as his knowledge is concerned. He has tricked-out everything from VW rabbit’s to Top Fuel cars. He has done complete 98 point restorations on cars such as ’74 Jag XKE, ’59 MB 190 SL, Porchse’s, American muscle cars, tricked out a Volvo to 27 psi of boost (TONS of internal engine modifications), tricked out my 1991 BMW 318is (stock 134 hp) to well over 300 hp with NOT A SINGLE PROBLEM in the 3 years it has been completed. He is now working on my
father's '72 Ferrari Dino. This only scratches the surface of what he's accomplished during his life and Corkey even said to me, even after the engine was blown, that Michael seemed to be the most knowledgeable person he has talked to with regards to the installation of this kit.
Corkey and I talked that Friday afternoon, but no resolution to the cause of blown engine was agreed upon. He was puzzled and I was in a total depression. We left it at that and said we would talk later when emotions were in order. As I hung up, I felt that no financial help was going to come from Corkey for the repairs on my car.
During the weekend I spoke to Andy Warren and a few times to Richard Friedman. I wanted to gather as much info on what could have happened, but mostly I needed an ear I guess (not one of my friends that tell me I spend too much money on the car…not what I needed to hear). I got phone numbers from experienced tuners that have worked with turbos on the NSX. I spoke with Jim from Mech Tech, Lance from Toyo-Moto, and Bob Norwood out of Dallas. It seemed to be unanimous that Corey’s Fuel system was very unreliable.
I told this to Corkey. I could tell he was not too pleased, and insisted that all his units are tested before leaving his shop. At this point I already assumed that I was not going to get his help on this and began to get costs for my repairs.
I’ve decided to go with the forged pistons at a 9.6:1 compression ration, a new fuel system from Mech Tech which sounds 10 times better, and my chip will be reprogrammed to retard the timing under � – full throttle. All the parts for this repair including all the gaskets, bearings, and the bore of the block will be about $4,000 US.
Now back to the call I just received. Corkey began by asking what I was doing to the car and I mentioned the above. Then he stated that he had time to reflect on what had happened and wanted to share it with me. At his point I though he realized that hey, not everything is built to perfection (fuel pressure reg.) and that he was gonna make things right somehow. I was wrong. He began telling me that he cannot attribute the engine failure to any of his parts and mentioned again that the fuel pressure regulator was tested before shipping to me. He continued by theorizing that Michael was
somehow responsible due to an "error of judgment" as he put it, during the road testing of the vehicle. He asked if Michael had a hearing problem and may not have heard the pinging during all the tests. When I told him I was in most of the tests with him he asked me if I had a hearing problem! We even had the engine cover off to make sure we could hear everything.
Furthermore, he stated that even though "legally and ethically" he had no obligation to help, that he had not decided on his participation in the repairs yet. Well, this is not what I wanted to hear! Even though his last statement would let one believe that he *may* help with the finances, I didn’t care anymore. Some people might have bit there tongue and said nothing, not to upset him. But I had to set him straight on a few issues and if it meant upsetting him and loosing whatever he was going to offer, I didn’t care… he was definitely going to know exactly how I felt about the situation.
First of all, I told him, Who are you to say that there was an error in judgment in the road testing of the car when you are all the way in San Antonio, Texas. On what grounds/evidence have you concluded this on? The other day he was praising how knowledgeable Michael was and now he’s saying that no one’s perfect. As if Michael has never heard what pinging sounds like in his life!!! Second of all, I told him what I thought of his quality control since he kept emphasizing that his fuel pressure regulator was tested at his shop. How could an $8,000 kit be shipped with SO MANY MISTAKES??? How could your quality control let this happen? They should have snagged these problems just like they would a faulty regulator right? No response from Corkey. If so many things were wrong with the kit (as mentioned before) it definitely makes it a lot easier for me to believe a regulator is at fault over Michael.
Things get even more interesting. I also told him that we were just following *his* instructions on how to fix/adjust the regulator. For 5 days we were fiddling around with that thing. Then he had the nerve to remind me that he said he was going to send another unit up. I had to politely remind him that when I told him that we would try his new suggestions one last time before making him send up a new unit he said "Oh thank you very much Eric, that’s very kind of you". I continued by telling him that being the professional that he is, he should have said "BRAKES ON…RED LIGHTS… don’t do anything until I send you guys a new regulator" (he agrees he could’ve said that). He continued by stating that if you saw you were not getting the necessary fuel, you should have stopped. That one didn’t go over to well with me either. I thought I was reminding him when I told him his own instructions say 80/90 psi of fuel for 5 psi of boost instead of the 95/100 that is actually needed, but I was actually informing him. He said "what?…the instructions say that?…well I’ll have to double check that".
I closed my end of the conversation off by letting him know I was not the least bit happy with his conclusion. It was down right insulting for him to turn around now and determine that none of his parts caused the failure, instead one of the most competent mechanics in the world cannot recognize pinging. And this is what he determined form his office chair in Texas….We are in Montreal, Canada by the way.
He closed off by saying we had cleared things off our chest and now are faced with a difference of opinions. (what????) He said he would call me next week to talk about it.
Well there you have it. This letter is not intended to personally flame Corkey or say his company is no good. But unless he can admit that perhaps *he* made an error in judgment by letting us continue trying things out instead of telling us to stop and wait for another regulator, AND… that his unit could have been faulty, I will simply say that Corkey Bell does not stand behind his product. In my opinion, it’s even cowardly of him to accuse the customer without having the remotest idea of what went on.
For those of you who ask why I am still keeping the turbo kit, All I can say is that the return for refund of the kit on UNUSED parts is 80%. I dare not ask what used parts are worth. I’m just going to make it work safely now. I’ve been told I can go up to 9 psi of boost with this new setup. You will find me hard pressed to go 1 pound over 6.
I am going on memory here since it’s been a full year since it happened. The damage was a seriously blown piston, a slightly damaged piston, and a toasted crank journal
I ordered/fixed the following parts: (Oh yeah, and by the way, EVEYTHING from Acura was backordered from Japan!!)
- MechTech Fuel System; Haltech F5 fuel management system; 2 extra fuel injectors
- New Forged lower compression pistons from JE (9.6:1 instead of 10.2:1). The original pistons on the NSX are press fit onto the titanium connecting rods and Honda/Acura sells them as a complete package (pistons and rods). You can imagine the cost of those parts, I believe it was in the vicinity of $600 per piston/rod. The cast pistons are cheap it's the rods which are really expensive. Therefore, it wasn't much of an option for me to go after market pistons. What I did was send all my pistons and rods to Jim at MechTech. He had the Rods machined so that a common floater system could be applied. The JE pistons cost me about $1,200 for a rush delivery. That's a $2,400 savings and a "safer" system than buying the stock parts.
- I replaced my Autothority performance chip with a chip supplied by one of MechTech's vendors to retard the timing under full throttle/boost. To be honest I don't know the mapping properties of this chip, I literally just took Jim's word on this one.
- My #6 crank journal was damaged so I went to a local place I know that works wonders. What he does is grind the damaged journal down 10 thou, then chrome it up to 20 thou and then shave 10 thou off the new chromed journal which brings it back to it's original dimensions. It's a very lengthy process but he does very good work and it's cheaper than a new crank.
- I needed to obviously get a complete set of new connecting rod bearings, and crank bearings. This was another "lengthy process". The crank has color codes for each half moon bearing for each journal (2 per journal). I was getting bearings from all over Canada and the US to match my crank (2 orange from Kentucky, 1 green from California, 3 red from Vancouver etc.) Also, if anyone is interested in finding out how much a complete head
gasket set costs, please make sure you are firmly holding on to something solid. It should come with a medical warning like "PLEASE DO NOT READ THE FOLLING PRICE TO A CUSTOMER IF YOU SUSPECT HE/SHE MAY HAVE A HEART CONDITION".
- I had to get my block bored out to meet the new JE piston specs. Luckily we have a tuner here named Zeke's. They are the ones that put out that special 315hp Firebird for the manufacturer. They do excellent work on engine building and blueprinting so my "fear" was limited.
- Just speaking with Jim at MechTech during this whole ordeal, he managed to pitch me into getting the new performance clutch as well.
Oh yeah, I forgot to mention that all the work was being done in my house garage :P. I bet most of you would have paid to see how we got the engine out of the car without a lift. To make a complicated story short, we dropped (not literally) the engine and lifted the car over it and put it to the side. Now, how was this done? With a lot of patience. We used 2 hydraulic jacks on each side of the front nose to "steer" the car and we used an engine lift chained up to the 2 rear strut mounts. We lifted the car so that it could clear the engine resting on the floor, and we placed the car down by the side of it. (There were some moments were my heart jumped a beat while the car was swaying from left to right 6 feet up in the air.)
The rebuild process was going quite well. We had finally received everything and Michael was so meticulous it was a sight to see. EVERY piece of that engine went into the tub with his "special cleaning formula" where he would scrub like a savage then air gun the whole thing out, and this process would go on 3 times for each piece.
The rebuild took a considerable amount of time only because of Acura and the back order parts. I was seeing my summer go down the drain (keep in mind, the car is stored for about 5 months here in Montreal. So this was really trying my patience and the Acura rep of Canada got an ear full a number of times).
When everything was in, the rebuild was a piece of cake (for Michael that is…I did the best I could, which was mainly passing him tools). The most difficult part was placing the car back on to the engine! This was harder than when we removed it because it had to be perfectly aligned while going down. We then setup the MechTech fuel system, and the car was ready to go (or so it seemed).
Here’s the bad news, to make a LONG story as short as possible, it seems that one of the connecting rods had become slightly oval when the engine blew where the bearings are placed. This was not noticeable while placing the half moon bearings but the result was spun bearings on that rod. At first we replaced the rod bearings (hoping that it was just that), but those bearings spun too as soon as we WOT the car 🙁
At this point Michael knew what the problem was, and took full responsibility. He sad that he had a feeling that the rod may have been damaged but was trying to save me money at this point and was "crossing his fingers" (and I don’t blame him, if you guys would have seen my state of being during this period you would have understood). Did I also mention that all the labor after the blown engine was no charge? He mentioned that in retrospect he should have done a bore gauge check <—(is that the right term?) to determine if the rod was still perfectly circular. At this point I said f__k it and got a new connecting rod (which came with the piston, which we removed and placed the JE piston on) and a new crankshaft.
Everything once again was back order. And get this, We ordered what is called a complete crankshaft assy from Acura. Do you know what this comes with?…NOTHING! Just the crankshaft (no bearings) so the hunt to find matching bearings once again took place. I asked the guy at Acura "how can you guys sell a crankshaft without the bearings and call it a crankshaft assy?" He was as lost as I was on this one.
Everything was put back together and I have done 4 track events since this catastrophe. The car is running relatively well. There are some issues which still concern me but it could be my paranoia kicking in.
Needless to say I have a lot more details on what happened during the aftermath of the blown engine. But 1. I’m not writing a book and 2. I need to save some interesting stories for NSXPO ’98 😉
Eric B. Kerub
eric "at" e-scape "dot" net
1991 BMW 335is (3 pages of mods)
1996 Toyota 4-Runner STOCK!! :P
1993 red/blk NSX s/n PT800001
Bell TT kit
Mech Tech fuel system
High Perf. Clutch assy (Mech Tech)
JE forged/lower compression pistions 9.6:1
ECU chip to retard timing under high revs and boost.
Comptech smog fittings
Comptech suspension package
Comptech sainless steel braided brake lines
Comptech Oil pump Impeller
Toyo RA1 race compounds (f:205-50/15, r:245-45/16)
RM brake kit (with 2 sets of pads---track only & street)
With Slotted rotors <------ NEW
RM front/rear Sway Bars <------NEW
RM Harness Bar w/Shroth 4 point belts <------NEW