Turbo VTEC questions

[timofytit]

I have a wreck of a Garaiya on its way from Japan(arrives this week) I have already started building a chassis and will fit the Garaiya body onto my chassis with a S15 Silvia headlights, Mazda Series 8 RX7 rear lights and some custome fibreglass.

The GT300 Garaiya is a race version of the street driven version in the pics below...

Chassis uses R32 Skyline adjustable wishbones, coil overs, brakes(R34), adj. castor rods, etc so I can fine tune the suspension. Should weigh in just over 800Kg and my engineer is happy to pass a 2L turbo as a street driven car with that weight/brake setup.

I am using my spare factory SR20VET engine but the engine is far from stock. It should hopefully pass all relevant testing though but time will tell. It will be on the dyno this week






Damn that looks sexy

Where did I put those Kleenex?

I want one

[Weq]

imhappy, i have no idea where u got the idea the low cam was bad for boost and high cam wouldnt spool a turbo, but you are wrong. Follow saxman's advice, its how we have been doing it for years. every engine is different, every setup will flow differently.

[iamhappy46]

I am basing that 'theory' on the stock SR20VET ECU mapping and switch points. It 'appears' Nissan did it this way to allow the car to pass the newer japanese emission laws and yet manage 309Nm of torque@3200rpm.

I am using the low rpm lobe to make the bigger turbo less laggy. The plan is/was to have the ETB restrict air flow to 0psi before 4000rpm, therefore I could have the car 'streetable' by shifting at 4000rpm and engaging the next gear at 3000rpm.

From there, I hope to gradually open the ETB from 4000rpm to 6000rpm with cam switch point somewhere in there, so that it builds boost/torque output gradually and remains driveable.

From 6000rpm to rev limiter(8000rpm) I an unsure how that will turn out, as there is so many variables in relatively unchartered Nissan territory.

The motor was on the engine dyno yesterday and got the idle to 4000rpm range tuned. Basic figures: 274Nm of torque at 4000rpm, with 115Kw@crankshaft without an alternator or p/steering pump load. Torque peaked at around 3600rpm with 288Nm on the low lobe only with only 0psi(had to trim the ETB back above 3600rpm as a boost limiter)

I doubt this turbo could spool up before 7000rpm running on just the hi lobe, so I believe a traditional 'intersecting the graphs method' would not really work in this application. Admittedly, I could switch the high lobe on at 4000rpm now and then see how the turbo spools from there, then intersect the graphs then.

Guess I am after an engine that is torquey, driveable and street/emissions legal but I will have a video/results late next week on how the engine performs.

[iamhappy46]

Have also been investigating fitment of a Honda K20A + FWD 6 speed + Hondata ECU to the chassis with JDM DC2 headlights/brake lights or something for the 'Honda connection'

Still using the Nissan double wishbone suspension but it should theoretically work with custom billet driveshafts to adapt the Honda inner CV's to the Nissan outer CV's.

[Dxs]

it looks sexy yet you are gonna put s15 lights etc on???

do a good write up of all this stuff man..
seems interesting

[iamhappy46]

Still building the chassis and the S15 headlights are about the only ones that are mass produced and would suit the front end design. I am open to suggestions on what to use though...

I have a 5 page writeup on the PGA forum about the car.

My only concern is camshaft selection, as I had 3 sets custom made and I am in relatively uncharted territory for a Nissan. I am currently on the middle set for testing purposes.

[iamhappy46]

The chassis has been built and the car has seen the dyno a few times already. Had trouble initially, as the rolling diameter of 19" rims and the gear ratios meant it had to be tuned in 3rd gear. This caused a lot of wheel spin(265/35R19) at any more than 9psi as the car still does not have a body. Weighs in at around 500Kg so it bucks a lot on the dyno, which has allowed the ratchet straps to break a few welds in the rear end

On 9psi, I was limited to 268.8Kw@wheels but running 16psi, some 17" rims, good quality tyres and using 4th gear netted over 350Kw@wheels not to mention broken chassis welds and a gearbox that makes more noise than a box of nails in a paint mixer

Currently chasing a new gearbox but my options are limited

Besides that, it handles alright with stock R34 shocks/springs, has plenty of go and lots of WHOA!

The front end is using 2005 Toyota Camry Sportivo headlights, Mazda 6 MPS brake lights and BMW 3 series guard repeaters. Should look nice once completed

[ProECU]

I doubt this turbo could spool up before 7000rpm running on just the hi lobe, so I believe a traditional 'intersecting the graphs method' would not really work in this application. Admittedly, I could switch the high lobe on at 4000rpm now and then see how the turbo spools from there, then intersect the graphs then.

Have you considered running the fuel fat at given rpm's and pull timing in those same areas to increase combustion temps and hence improve spool?

Your tuner should be advising you of these techniques.... if they know whats going on of course.

[iamhappy46]

Trying to pass exhaust emissions so that was not an option. It appears to be working well now although the drive by wire technology makes the system a little 'doey' going from closed throttle to 'full accelerator pedal' and waiting for the throttle to open. Makes it jerk a little but some fine tuning might get rid of it.

I should mention that I am using E85(85% Ethanol) which appears to be working well. A lot cheaper in a 44 gallon drum than my local petrol prices

There is a video available of the car on the dyno as well. Let me know if your interested in viewing it

[ProECU]

yup, interested, link me

[Zilli]

link would be nice

[silver_screen]

Im assuming that its a 4valve per cylinder engine just like all the other sr20s... I read that u were sayin something about running on just the high lobe?? My impression (havent seen a sr20vet yet) was that the rocker arm is locked into place via oil pressures or electrically to ride the hi cam... which means that ur low lobe isnt connected.. the hi lobe moves 2 intake valves to let air in.. having the smaller lobes runnin wouldnt work because they move the same 2 valves... plus once runnin on the hi cam the small lobes wouldnt b able to touch the rocker arm regardless. What turbo r u thinkin of using?? I was goin to run a GT30R turbo on my last NORMAL sr20 and that wouldve made plenty boost well before 7k... I havent had much tuning experiance but turbo selections and engine buildings i do pretty much every @ work and at home... stock cam profiles r kinda nice too lol