Boost dropping off so in turn Power and torque dropping off in a major way after 5k, i have persistantly had this problem with above 5k boost for nearly a year now but as this has been the first dyno run which i understandably wasnt too thrilled about.
229 bhp im gutted, my old 1.8 itr had 200bhp on the rollers
I have changed the intake pipes to solid type and pressure chamber check valves, car is bone standard except hks filters and cooling plate and a nur spec backbox.
Someone must have had this problem before please help me out, otherwise its a long 600 mile round trip drive to jimmys who rebuilt the engine and turbos 6k ago to have an eyeball.
rotary experts HELP !!!!!!
(http://i9.photobucket.com/albums/a66/neil_jdmr/IMGP0818.jpg)
(http://i9.photobucket.com/albums/a66/neil_jdmr/IMGP0819.jpg)
anyone ??????.
dont think its a boost leak as first tubby is spot on
Could be a dodgy solinoid, cracked rats nest pipe (vaccumm pipe) or bad one way valve. Do a quick search for boost issues and you will find there are absolutely loads of useful threads :D
Hope this helps :D
Shaun
are those figures flywheel or wheels?
if thats atw its about right.
matt
Flywheel figure fella\'s and definately not right also i have searched and searched throughout this site and fduk/rx7club and nothing seems to match this problem.
as you can see in the graph the second turbo pulls hard after the transition but dies off after 5k and this matches my boost dropping off.
the torque just gives up at 5k
All other fd\'s ive been in boost solid and pull hard to redline
you may be getting things a bit muddled that is a power graph isnt it!!???
that is not a measurment of the boost you are getting.
i would start thinking about checking maybe your fuel pressure whilst having a dino run or matey even start checking your spark as either a weak mixture or weak spark can cause a drop off in power higher up the rev range the way your power graph is showing.
if you have only had a power run and not a setup run by an rx7 specialist then i would reccomend you do so as they will check these things whilst carrying out power runs on there dino it would def work out cheaper for you in the long run.
Did they give you a AFR graph as well, see what thats doing up the rpm range , could be a few things, Ignition break up at the top end,Fuel problem,too rich at the top end therefore killing power, do you hold 10 psi till 8k rpm?
It was just a power run but i have been watching my boost drop off at the same place on my boost gauge for some time now.
If it was a fuelling issue wouldnt i get the heat light flashing to indicate high knock levels, i do not get fuel cut or anthing like that also its a standard ecu so is running rich as standard anyway ????
Blitzboy - No the boost drops at 5k to 6-7 psi
ahh so if the boost is dropping to 7psi you would be losing a lot of power, 7 psi is wastegate spring pressure on twins, so this would indicate a Rats nest problem imo
Looks like we\'ll be doing your rats nest when we check your solenoids then bud! Best make a weekend of it then
first weekend in aug do ya rob ???
I had this problem with my old FD... Turns out that it was the intercooler pipe on top of the standard cooler... There was a tear underneath and only when the boost was high enough it leaked... Replaced with Samco hosing and it fixed it..
this also happened on my mates FD as well...
Other than that i think you have a problem with the rats netst :(
I\'ll have to check with the wife but i think that should be ok bud. We\'ll try the HKS hard pipes also going on what AndyGen3 has posted. I haven\'t got any connecting hose tho so we\'ll need to get our hands on some to check. It may be worth checking that first off as if it is that then it should only be a few mins to get sorted. Anyone know the diameter of the I/C connectors on a standard i/c using HKS hard pipes?
dito andygen3.
but surely u\'d hear it. I did on mine. sounded like someone had put 40 hairdryers under the bonnet at 5k rpm.
i\'m still voting theres something up with your pressure chamber vac pipes. maybe a small split or leak cos it sounds exactly like sympton 3:
| Primary Only | 4,500 RPM | Primary and Secondary | Check |
| Solid 7 psi | Solid 7 psi | Solid 7 psi | Missing pills for Wastgate and/or Turbo Pre-Control Actuators. Wastegate and Turbo Pre-Control Solenoids are elctrcially unplugged.
|
| Spikes above 14 psi | | Spikes above 14 psi | Hose from Primary Turbo Compressor to Wastegate and/or Turbo Pre-Control Actuators has popped off. |
| Solid 12 psi | | 5 psi or less | One of the vacuum hoses connected to the pressure tank, pressure tank chack valve, or hose between turbo and check valve. They will come off again unless the hose is replaced or zip-tie it at both ends. |
| Hear boost leak | | Hear boost leak | Y-Pipe coupler |
| | | | |
i had the problem with the check-valve. replaced it. then the pressure blew a split in the intercooler pipework.
Its not symptom 3 matey as ive changed all those hoses and zip tied them on and also replaced the check valve to a working vitton valve.
Did you get some new viton valves bud? If so where did you get them as there is a fella on here looking for some.
It\'s def not symptom 3 like, you do get full boost after the transition but it tails off after 5k, i\'ve a feeling there is a split or something that is venting boost once the transition has taken place. We\'ll find it fella!
Mine had cracked on the vac-lines between the turbo and the water pump (under the air pump). There is an extension off the rats nest that drops down around the water pump bottom hose near to the OMP.
Only found it when I pulled the bits out for the single turbo.
Shaun
you say its stock, do you have a cat?, if so, i bet its blocked! that would create all the symptoms you describe
The cat is near new mate i have removed it and its perfect no rattles nothing, i even bought a spare to try but my one was in much better condition than the spare i bought.
weekend aug 2nd rob if thats cool with you, how much vac pipe do i need ie 4mm and 6mm for the rats next also 70mm for the hks hard pipe intercooler pipes??? is that right.
Ill try get hold of Chris as he had some intercooler pipe i could buy that he doesnt need i believe,
Thanks for all your help though guys ill keep you all posted.
Hi bud, just realised that i\'m working the sat of that weekend, so can we do it the following weekend?
Have you changed the plug leads? Had a similar prob years ago with power tailing off after 6k. Replaced plug leads for Magnecor ones and sorted prob.
Jon