fd3s400438

Hello there just a quick one. I have about 470 bhp to the engine. The car has an aggressive port , HKS single TO4E , HKS downpipe with the EWG gas being dumped back in the exhaust and from there its a 3inch all the way to the back

I am not sure if it is 3 inch outside or 3 inch inside diameter because a 3 inch pipe may be 70mm internally

Anyway although I hava an profec b and an HKS external I get alot of boost spikes and was wondering if my exhaust setup is a bit small for my engine

Small turbo with quick spool up + small exhaust = alot backpressure = boost spike

I may be wrong of course. Any of you people running 500bhp motors what internal diameter exhausts do you use

Thanks alot...

MaliciousMD

iTrader: (1)

Not a 500HP car here, but what waste gate do you have? Size? How big is the dump tube back into your exhaust?

arghx

iTrader: (3)

The HKS cast manifold is bad for boost control.

RotaryEvolution

iTrader: (30)

so is plumbing the wastegate back into the exhaust when pushing that much from that size piping. dump it to atmosphere and you will notice it will be easier to manage.

fd3s400438

Ok so far I have re raouted the exhaust gas grom the external WG from the downpipe to the road as an open WG

I did notice that the boost is more manageble BUT the boost control does not respond on the SET setting

What I mean is this...

I have set the HKS WG to 1.2 bar from the adjustable screw...So with the boost control OFF I have in 3rd gear 1.25 - 1.2 bar which is about 18psi

I tried setting the gain between 5 and 10% , my start boost between 11 and 13psi and no mater what I dial in the SET value I will not get a decent rise in boost

My target is between 20 and 22 psi . I have to raise the SET all the way up to 70% and still I only get about 17psi in 2nd gear , 19 in 3rd gear and 20 psi in 4rth gear

And this is with 70% SET when with the boost control OFF I have 18psi in 3rg gear

All boost line fron the WG , selenoid , manifold etc have been changed , checked and rechecked

If there a case that my small HKS T04E cannot handle more boost and no matter what I dial in it cannot give me more

From my understanding if the boost control OFF give me 18psi I should be able to achieve 22psi with only 25% SET and I have reached 70% and still it doesnt feel strong...

Rob XX 7

iTrader: (8)

Profec b spec ii?

Read this, i suspect you might need to play with the controller a little
https://www.rx7club.com/2nd-generati...-chart-952769/

RotaryEvolution

iTrader: (30)

may also be a configuration issue, some controllers have 2 settings. 1 for internal wastegates and 1 for externals which are plumbed using different ports on the solenoid and will give different results with controller adjustments. if the plumbing isn't setup right either that can cause the controller to not give much feedback.

Rob XX 7

iTrader: (8)

sounds like a set up issue.
I also have a small turbo HKS wastegate and manifold and when we tried to retune for e85 I wasnt holding boost but no spikes. I had a bad diaphragm and also needed to change the spring.

I found that profec spec ii a little tricky to understand the instructions but once I started messing with it I actually really liked it. The link above is a really good in write up for it. Check your routing and set up then take a good look at your boost controller settings

fd3s400438

I have been using Greddy profecs since the very first model without the LCD screen. I know my way around them and all hardware has been installed correctly. Com and NC ports have the correct lines from the WG and the turbo compressor etc

I seems very weird because the car runs like a dream with the controller off. 18-19 psi in all gears no matter what revs I have whn I decide to go flat out.

By turning the boost control on and using the following setting all that seems to be changing is the constant boost again at 19-20 psi.

Set : 65%
gain : 5 %
Start boost 0%

All I get is an '' overboost '' or spike that comes close to 22-23 psi and then it fades straight away back to 18-19 psi ( more or less my WG spring setup )

Is the a chance that the T04E is not big enough to flow more than 18-19 psi constantly ???

The engine is race ported , ceramic seals , lower compression ratio ( 8,5 : 1 ) , 550s + 1300 and all the usual expensive auxilery...

More or less I built a boolet proof engine that can take 550hp + using the smallest turbo available back in the days ( 2006 )

fd3s400438

Rob xx 7 my problem is the exact opposite from yours. My boost is NOT dropping of. WG spring will give be 18-19 psi all the way to 8300rpm BUT the minute I switch it on all I get is boost spikes at low rpm while flooring it...

The constant boost at 65% seems to increase from 18psi only up to 21 and this is only in 4rth gear. 3rd give me more or less WG spring boost ie 18-19 psi

Rob XX 7

iTrader: (8)

if i can boost 20-21lbs with my tiny turbo I cant see why yours would be a problem

you said it yourself- going off wg spring there are no issues, when you use the controller it is not right- there is a problem with your controller settings or the solenoid

have you tried the gain at 0 to see if it changed anything?

RotaryEvolution

iTrader: (30)

then i believe your problem is in the port configuration, i always use the COM and NO ports, NC is vented to atmosphere to release line pressure to raise boost.

fd3s400438

Yes but if you look the diagram for an External wastegate setup it uses the COM port on the External WG head and the NC port to the compressor housing for a good boost source...

Isnt the diagram you are showing for an internal wastegate setup???

fd3s400438

If I had a diaphram leak would the car still produce a healthy 18psi only with the WG spring BUT behave funny with the boost control on???

Last night I dialed in SET @ 75% , gain 5% and start boost 0.5 bar and I only got 20 psi in 4rth gear... So only a 2psi raise with 75% dialed in

Something is not right...

Rob XX 7

iTrader: (8)

I had a leak and it wuld only affect higher boost, basically it couldn't hold