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Turbo set and parts
Honda NSX Turbo

AMS/AMW  NSX Video :


Max effiency Turbo build, Juha Martikainen, November 8th 2016


As a professional car /engine builder I was looking for car to work with in 2008. At first I was looking for Toyota Supras but I had seen so many of them in my dyno so I lost my interest. It had to be something different that I had seen so far. And so it was! I bought Honda NSX as a “test bench” car in 2008. It was a very good purchase!


I have been working with turbo business for over 30 years so I might have a different perspective to do things than people who normally do their NSX. I have been working in dyno about 8000 h and tested countless number of turbos, engines, exhausts, ECU’s, injectors, pumps, etc.


Turbo or supercharger? Turbo is the only way to go in these days! But only LOW BOOST!


Everything under 1 bar over pressure (14.7 PSI) is LOW boost setup. If you have a good engine, about 80-100 hp/liter, it is a good starting point for low boost /high power system. At 1 bar boost level you normally double your NA power if everything is done right! It is too easy to make lots of power these days! So what I was looking for was maximum total package efficiency less than 1 bar. So let’s go …


Engine power is true crankshaft power. Stock 1994 Honda NSX has 268 hp on crank.


My Honda NSX engine setup now is as follows:


-1. Build engine with CP/Carillo, Cometic, Block quard, stock cams, Toda oil pump, steel main caps


-2. Compression ratio 10.9-11:1 (OEM 10.2), rev limit 8250 rpm.


-3. Engine management HKS F-con V-pro 3.3 (Pro shop) 32 bit ECU. Closed loop wide band.


-4. BOSCH EV14-1200 cc injectors (Finjector) 2x Bosch 044 fuel pumps in tank.


-5. Garret GT4088, journal bearing turbo, twin scroll, 1.09 or 1.19 turbine housing


-6. Tial 60 mm wastegate, AMW dump valve


-7. Headers 3-1 309S material ID 36 mm, 1.42”, (OD 40 mm), Y-pipe is 316, ID 41 mm (OD 45 mm)


-8. 89 mm 304/409 (3.5”) light weight exhaust single output to right side, WG output is left side


-9. Garret IC water /air 1000 hp core


-10. Main trigger wheels is on crank


-11. CAM timing done using OEM gears + offset pins


-12. Bosch COP coils, NGK 7 BKREIX spark plugs


-13. HEAT management


-14. Mapping


-15. Oil cooling OEM


-16. Summary of all modifications


Let see closer look of details:


1. Steel Main caps, Block quard done in 5 axis mill. Very tight tolerance. Bearing running clearances OEM “loose” side. All machine work done my friend Mika. Good machinist is worth of gold! Next engine block guard or Darton > darton less blow by.. much less!


2. Why so high Comp ratio, 11:1? There is no reason to lower it if the boost is under 1 bar and heat management is done correctly! Lowering comp ratio will affect engine efficiency in a negative way: poor throttle response and weaker exhaust pulses in tubine side. Strong pulses are better for turbo turbine side. This is the way to go with these amazing engines!


3. HKS ECU. Our shop has HKS Pro dealer status, so it was a natural choice. 32 bit ECU with damn good and stable inputs, high resolution, closed loop lambda control.


4. Modern Bosch injectors are only injectors what we are using now in all our customers cars. Bosch 044 motorsport pumps in fuel tank. One is placed in OEM location, one is in side of tank, inside tank foam! So foam holds it in place.

5. Turbocharging is all about turbine side pressure control! Whatever system you do, you need to keep exhaust pressure under boost pressure. Or at least try to do it so! Some people may say it is not possible but it is. This rule is part of this high compression ratio chosen for. If your turbine pressure is lower than boost, flow is forced to go all the time right direction, out of exhaust valve to turbine. So you are filling cylinders perfectly! When exhaust pressure crosses boost pressure (goes over), that is point you start losing torque! IN every engine same pattern! This setup change crossing point 500 rpm higher. This means fresh cool charge in every stroke, you can run very high timing numbers and this will help to keep exhaust temp low and you will see amazing power numbers.


Now let’s look what turbo has good exhaust side up to +700 hp. Garret GT4088 has biggest turbine wheel in this category. Normally stock Garrets are poor sized on turbine side! This turbo has “Good” Turbine/compressor size ratio. It should at least 1:1. GT4088 has 64.7/88 (88) in compressor side. Turbine side is 70.6/77mm, so ratio is 1.09. I think perfect turbine for this setup could be (small diameter) 73-74 mm. APT has special V-band output turbine housing for these and this is biggest turbo what you can physically use, very limited place over gearbox/trunk floor where this turbo is located in this setup.


First testing this turbo from box with 1.09 exhaust housing gave 403 hp at 0.25 bar (3.6 psi) so over 120 hp with only 0.25 bar! And boost rise and response were very good. Exhaust pressure data was not ideal because turbo was “out” of compressor map! Turbine side was lack of energy in this power level but still numbers are quite good. I could choose BB unit but what I have seen it does not play a very big role, if the rest of things are done right. With this setup your turbo is using exhaust pulse energy well, so you get max out of it. You should have twin scroll turbine like this turbo has. As you know compressor/turbine wheel share same axle! Whatever you do (or not) it will have effect on both sides!

I have made some changes to turbo Garrett GT4088 unit to make it better match to Honda engine. Some developments, like bigger diffuser area and smaller compressor (bigger diameter from 88 mm to 78 mm). Originally this Garret compressor map extends up to 3 bar pressure level! We need only 1 bar, so bigger diameter of the compressor wheel can be reduced. It could be as small as 72 mm by turbo specialist but I was not so brave to make it so small. So I made only bigger diffuser cap, it lead to lesser drag, more air flow and lesser turbine pressure because turbine does not need to make so much work.


Oil flow is reduced to turbo. There is oil jet before turbo, only 1.5 mm. C30A has high oil pressure and I am running only low boost and avoid any smoke from oil burning in your turbine this will cure the problem.


6. Tial 60 mm wastegate. You need bigger wastegate to control boost in this low pressure exhaust system! Now you need to get pulse out, not pressure.


7. NA headers are for NA cars, not for turbo cars! Primary diameter is in this set only 36 mm ID (1.42”). It could be smaller, but this is best size for this power level. It will be good over 1200 hp. You primary concerns is always turbine sizing. Turbine is the place where you make your exhaust back pressure! Small primary has fast flow > secondary pipe is 41 mm ID same rules, high flow is need for turbine. Bigger is not always better in this area. 309S is one off the best material for turbocharger headers. Next best is Inconel but it is only for big money race teams. Turbo is connected to side of gearbox. It does not move so there is two special flex joints in both secondary pipes. Wastegate outputs are in outside corner of bend to get exhaust pulse out of turbine. Screamer pipe is 63.5 mm (2.5”) T4 Flange is 12 mm 304.


8. Exhaust pipe after turbo has to be as big you can make! 3” is good up to 500 hp. If you have screamer pipe after turbo unit, 600 hp is max. Over 600 hp you need 3.5” (89 mm) or 4” exhaust pipe. Back pressure after turbo has to be less than 0.05 bar so bigger exhaust pipe is always better! My Honda NSX setup has 89 mm (3.5”) exhaust and it is only 1.5 m long. Handmade straight thru SS muffler is used. Tree layers of absorbing material provide excellent exhaust sound!


9. Intercooler front heat exchanger is only 16 mm thick. 250 mm tall and as wide as frame rails. This16 mm thick core does not have effect into engine radiator. Intercooler coolant temp is only 1-5 oC degrees above ambient (Celsius). Bosch coolant pump and 15 mm ID hoses. Hoses run in tunnel and these hoses are in polyurethane insulation foam tube. Tunnel gets very hot but this polyurethane tubing blocks all heat which may cause problem. Part of heat management. Works damn good. Heat soak is problem, if car does not move but I run pump always when ignition key is on this helps.


Intercooler end tank design is critical! If you don’t pay attention, air flow goes through the core using only 10% off its surface area! There is no point to make 10% charge cooler.


There is two ways cure this problem. Using spoilers inside entry tank. It does not harm flow much but this way you could reach “flat” flow through core. It could be tested using a “garden” blower.


Put only entry tank on using duct tape. You feel how air comes out of core. Or hard expensive way making high flow end tanks like race cars has (pictures are coming soon).


10. C30A has some problems on crank trigger which is located on cam shaft! System works ok when engine accelerates fast. Gears 1st to 4th there is no big problems but when you chance 4th to 5th or using 5th gear, there is point when cam timing system has huge vibrations and that causes timing errors to engine. When testing a car on 2 mile runaway place you can feel it, data logger has rpm movement 50-120 rpm. Problem is always in same spot 6800-7200 rpm. I made new trigger system on crank and now problem is solved and disturbing rpm movement is only 0-20 rpms (according to HKS datalog value). CAM reference point (sync) is still on cam. With new trigger system rpm signal is very stable at idle up to rev limit, you can feel it and hear it! BUT problem is still there! Cam timing error does not go nowhere, but now your crank timing is perfect and steady.


Let’s look at cam gears. 4 gears and all these are different by weight. Front blanc 4-5-6 exhaust gear is light so is the intake RR 1-2-3. FF intake gear has timing sensors for both blancks (weird). AND RR exhaust gear is SOLID STEEL. This is clear evidence at this engine had problems on this area. Heavy gear on RR exhaust cam has some inertia so it dampers vibrations (last one before crank gear). It will do its job but it is not perfect! So are you “smarter” than HONDA R&D? (If using Lightweight gears). Same way all engine manufacturers do, nothing new. But normally used on diesels on low speed.


11. CAM timing after thinner head gasket and head bloc surface. After this operation cam timing could be way off! Cometic head gasket is 0.76 mm, OEM is 1.22 mm + 0.1-0.2 mm surface head and block 0.1-0.2 = total “deck” height could be now – 0.66-0.9 mm! Distance to first cam gear is now reduced 0.7- 0.9 mm, not real bad but RR intake is now 0.9+0.9+0.9 = 2.7 mm OFF! This can be corrected only ONE way. Offset studs on OEM cams gears. Using light gears you could find something “new” from your engine! Not recommended! If you have lathe, it does not cost you nothing to make 5.00 mm offset studs. Or local machine shop can make those too. I made new studs using Mitsubishi EVO main bolts :) You may also use old ARP studs or very strong universal bolt about 10 mm. You need two studs. One to FF exhaust cam gear 0.3-0.5 mm offset. And one to RR intake 0.9-1.2mm offset. But every engine is different so there is no correct offset. It will take 2-6 hours to make it perfect.


Normally I just lock cams using self-made pins. Before I lock cams I will check that timing marks are perfect. Normally these locking studs/holes on cam are very close. I have also a couple offset pins if there is misalignment (by shop manual).


12. Stock coils with fresh spark plugs capped to 0.6 mm are good up to 650 hp. With 0.4 mm air cap you may get 700 hp but this is never tested. With Bosch AMW cop coil set old spark plugs capped to 0.6 mm you will run what number you want. In spring 2016 I used 2000 km driven spark plugs with 0.6 mm air cap I could get only 560 hp and then I got misfire. I have 4 set of old NSX coils. Nothing helps. These Bosch cops engine starts easier, revs like a dream, feels damn sharp, NGK spark plugs are very good quality plug to use so it was my choice. These spark plugs have 5 kOhm resistor: use resistor spark plugs only!


13. Radiator on front/engine middle. Perfect for heat management! Temperature of the engine surface is 78-90 oC degrees. There is nothing what you could do for it. Exhaust surface is 750-900 oC degree and it is easy to cover it something, nowadays there are plenty of solutions. In my case headers are covered with ceramic heat blanket, Y-pipe has “thermo” tech style wrapping and turbo has ceramic fabric jacket. Charge cooler is located top of transmission and side vent is pushing fresh air into engine bay in that area. Air filter is in same place, front of transmission. So all exhaust heat is going to turbo and then out of exhaust tip. Less turbo lag. Less heat on engine bay.


Intake heat can be reduced using heat insulation between block valley /intake manifold. HUGE gain! It is good idea to use heat spacers between head /intake flange. But this area is only 5 % of total intake surface! Block valley is DAMN hot barbeque.


I have a multi-layer blanket in that area. Ceramic fabric, polyurethane foam and aluminum covered fiberglass.


This way engine bay gets so cold that you will have problems with you breather hoses on a cold day. Cold day is under 17 oC deg. Oil, water and fuel mix cools down in you breather system and may get blocked! If you have cotton filter, it will block for sure! Needs regular service!


14. Mapping is for professionals only! One wrong hit on keyboard will blow up your $20 000 package. Maybe not in dyno but on street or track. This is when experience comes in handy.


Leave always some safety margin when tuning engine. Use datalog! AFR, oil temps/pressures, air temps ext. Use warning lights!


After dyno, play wise with compensations! You can fill up 8-10 mm extra oil in pan. This may help in corners. OIL pan baffle is MUST!


15. External oil cooler is bad idea if not using huge hoses! Even AN12 is too small! I will get back to this item later on.  Best idea is the use external engine coolant cooler instead OEM engine oil cooler. But I will work on that later on. I have all parts for it. I did external set so I have cooler and carbon duct from that project.


16. All ends UP. Fine tuning is like circle. Even small chance will affect something else and will end up big gain! But if you choose supercharger/blower not belt driven Rotrex with good intercooler, there is no way to overcome intake heat problem! And this is circle what goes opposite way could be disaster. It is very hard to tell what is the biggest problem on C30A or turbo setup but I would start choosing correct turbocharger to way I just wrote. There may be even better match than this Garrett GT4088. And I am looking for better option ….


IF this is done wrong way it can’t be solved. Headers, exhaust pipe, cooler. All play they role so all these must be correct.


Change crank trigger to crank shaft, use Bosch cop coils. Wise tune! Safety margin not pull too much ignition of from base map after dyno. Don’t wash your cylinders! 11.5 AFR is super safe.


Be sure that your AFR meter (air/fuel ratio) is giving correct numbers! If is it placed too close to turbo or high pressure area (exhaust back pressure) it will not show correct numbers!

Increasing boost give more power. Normally you can double it with 1 bar boost, as I stated above. Latest values are amazing 711 hp/PS at 1.05 bar (15.22 psi) 728 Nm torque, 98 octane pump gas (5 % ethanol). 2.65 times more than OEM NA application! 

2017 Turbo set up

T4>macined to 3" v-Band ! 

High Flow intercooler ( option only !)

Old style  exhaust 

BoschEV14 500-1550 cc

HKS F-CON 3.3 PRO Ecu + supporting electronics ,TECH EDGE Lambda and 1 mb Logger (read: all goodies)

NSX water-air intercoolercore