Jump to content
SAU Community

Recommended Posts

Sorry to bring up such an old thread but im currently in the process of building a RB30DET (Forged 3.0l Bottom end, RB26 Head, GTX45, E85, Built C4). My engine builder has told me we want a 11.5:1 compression ratio because we are using E85. ill be looking to run 30+psi with this. Ive contacted Brad @ Spool Imports to see what pistons he can get his hands on that would get close to this CR. He reckons that they (CP Pistons) wont be able to fit enough Dome on the piston to achieve that. Another issue im looking at is, ill be running fairly high lift cams (between 9-11mm lift) so with such High compression im assuming ill have to fly cut the pistons which would lower the compression again surely. So what CR have people running high boost and E85 run and how did you achieve that CR (original CR of piston, work to block, HG thickness etc)?

you're really in unknown territory there mate. I don't think anyone could give you advice having been in a similar situation. 11.5 CR is stupidly high for a 30+psi goal Internal cylinder pressure is going to be incredible, hope you've got strong internals.

Cam wise I'm sure someone could weigh in, you can measure the valve movement and height of the piston so surely clearance can be worked out beforehand

Yea the motor is being built to go for the 850+rwkw so alot of people seem to be very quiet in regards to advice. my builder has a lot of experiance building High HP and high boost motors, and to my knowledge hes built 2 RB30DETs and both went 600+kw for years so i trust what hes doing. just interesting to see that no one else has gone big power with high comp on E85.

Yea the motor is being built to go for the 850+rwkw so alot of people seem to be very quiet in regards to advice. my builder has a lot of experiance building High HP and high boost motors, and to my knowledge hes built 2 RB30DETs and both went 600+kw for years so i trust what hes doing. just interesting to see that no one else has gone big power with high comp on E85.

is your builder from tas by any chance

Yea the motor is being built to go for the 850+rwkw so alot of people seem to be very quiet in regards to advice. my builder has a lot of experiance building High HP and high boost motors, and to my knowledge hes built 2 RB30DETs and both went 600+kw for years so i trust what hes doing. just interesting to see that no one else has gone big power with high comp on E85.

You would think there has to be a good reason for that.

I take it your engine builder has not used astronomical compression ratios in his previous 600w builds otherwise you wouldn't be asking how to acheive it.

I be questioning the engine builder how he is going to run 11.5, over 30psi and achive it with removing the squish pads from both sides of the combustion chamber to handle those power levels and DET and still remain at 11.5.

Oh hell, did i just drop a spanner in all the works by saying that? :)

There is someone in the US from memory who has a CNC machined open cumbustion chamber design with a custom domed piston to suit, still not near where your engine builder wants to be compression wise.

Most builds in your power bracket are running flat tops with open chambers, so very low compression then winding copious amounts of boost into them, usually in the low 8 compression ratio.

If your engine builder wants 11.5, ask him for the piston part number or to organize to get it custom made......

  • Like 1

I don't know why you would do it just to get a handful more hp off boost; you are fuel constrained (or more specifically octane constrained).

More info on NYTSKY's mate would be interesting!

I don't know why you would do it just to get a handful more hp off boost; you are fuel constrained (or more specifically octane constrained).

More info on NYTSKY's mate would be interesting!

I'm not sure I agree. I reckon that no-one really ever gets close to using up all the anti-knock property of E85 just by winding up the boost and adding timing. You have to stop adding timing a fair way before you can make most E85 engine knock simply because you stop making power.

Trying to use up the knock margin by taking the easy option of just piling in massive boost is unlikely to be better than starting with a more capable base engine (more compression) and adding less boost. Boost is bad. Every psi you pump the air up adds heat that you have to cool out of the air. Every psi that you add to the air is also pretty much added into the exhaust manifold. That adds exhaust contamination back into the cylinder that doesn't have to be there.

I reckon it is smart to try to find how high you can run static comp + boost on E85, still get realistic ignition advance numbers, etc. More static comp is going to make the engine more willing to work off boost and very much improve the boost threshold. What's not to like?

  • Like 1

I'm not sure I agree. I reckon that no-one really ever gets close to using up all the anti-knock property of E85 just by winding up the boost and adding timing. You have to stop adding timing a fair way before you can make most E85 engine knock simply because you stop making power.

Trying to use up the knock margin by taking the easy option of just piling in massive boost is unlikely to be better than starting with a more capable base engine (more compression) and adding less boost. Boost is bad. Every psi you pump the air up adds heat that you have to cool out of the air. Every psi that you add to the air is also pretty much added into the exhaust manifold. That adds exhaust contamination back into the cylinder that doesn't have to be there.

I reckon it is smart to try to find how high you can run static comp + boost on E85, still get realistic ignition advance numbers, etc. More static comp is going to make the engine more willing to work off boost and very much improve the boost threshold. What's not to like?

That is the same thoughtI had up until I talked to some serious enginer builders; I explained exactly that and all dismissed it stating their experiences. It makes the engine more prone to issues with excessive squish velocity and the handful of hp made off boost was offset by the much larger increase in performance by increasing boost pressure.

I agree there is a balance, but it would be dependant on application as with most of these decisions.

There is a simpler way to get the static CR up and it's as simple as using an RB25 Neo turbo head - smaller volume combustion chamber .

It involves changing manifolds or fixing points but if you want super power it can be done .

I agree that extra fuel octane is great but the point of it is to have the optimum ignition firing point for most power rather than finding the limits of the fuel .

As per boost thresholds I'm not sure higher static CRs will bring them down , more likely increase the pre and just post positive pressure torque .

My mentors taught me that there are two benefits of high static CRs .

First , the only way to increase an engines power other than FI revs and capacity increase is the static CR .

second , it's the way to reduce the torque loss (reduced dynamic compression) on an engine with long duration cams .

Thing is that really high cylinder pressure and power loads means having the engine structure more like a diesel though if anything they are worse off because they make comparatively big torque at low revs . It may not be silly to search what Nissan did to RD28s to make them a reliable diesel .

A .

Has anyone had failures from using E85, from what ive read, E85 being an alcohol cleans and washes the cylinders so with a lot of compression/boost and increasing piston clearances from forged pistons or worn stock pistons I wonder if there could be an increased heat and friction build up to cause a piston failure. Could this be possible on an RB30 piston that doesn't have the oil

squirter to help cool the pistons or does the amount of oil outweigh the ethanol content in the cylinders.

Edited by AngryRB
  • Like 1

E85 engines run MUCH cooler than petrol engines. So your worries about heat issues are unfounded.

E85 does clean up all the crap in the combustion chamber and so on.....but not from "washing" as in wet fuel washing like you appear to be worried about. If it was wet fuel washing the bores then you might worry about reduced lubrication, but the cleaning action is actually from steam. So I wouldn't fret there.

There is a concern with old tired engines or engines with forgies that have been built too loose (as in they don't actually need to be built as loose as a lot of people think they do, and if you make the mistake of building it very loose, then yes, it will be loose enough to possibly permit this concern to occur) then you can get a lot of blowby into the oil, and E85 blowby is full of water. So that can upset the lubrication and possibly lead to failures. But it's not because of heat. The absence of an oil squirter probably not an issue given the lower heat issues with E85 - but any potential lubrication issues from water in the oil are a separate issue that may or may not be assisted by having a squirter - as in, I think if the oil has enough water in it to be a problem, the a squirter probably won't help anyway.

Edited by GTSBoy

I know that engines run cooler, my point was more that if lubrication was being lost from the alcohol's cleaning effect then there would be increased heat build up around the top comp ring as friction increases with boost/comp.

What piston to wall clearance would you suggest if dedicated E85? I was thinking a 4thou could allow washing down the skirts on cold start?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • My experience with Rising Sun Exports Before agreeing to the sale I tried to do as much research as I could (obviously), his Facebook reviews are 98% and he goes Live at least once or twice a week. I contacted 2 people in the UK who had used him for their imports, both had positive feedback. His explanation and talk through of the import process was thorough, answering any query no matter how stupid it was. It felt as soon as the money was sent, communication dropped off. I asked for shipping updates every 2 weeks or so, not wanting to pester him, he never had any updates. I wasn't informed the car had been dropped off at the port, I only found out by his Facebook story. I asked for the photos taken at the port, knowing he would need some for insurance purposes. I received a few 5 second clips and that's it. When asked again, he said his staff had them. Weeks later I asked again, he tells me he doesn't have any, but does have 50 photos from the original advert. I never received them. I eventually got the documents sent via WhatsApp after I mentioned the port was requesting them. I purchased a CarVX report, to find out the vehicle is a Grade R with recorded accident damage, first recorded in 2017 when it was first auctioned. He never told me the grade, then again I didn't ask. His response was "Grade R means nothing, it wasn't chassis damage". Still, I would have liked to have been informed about it. Jon prides himself on being open and honest when it comes to inspecting cars, it's his main job doing so at the auctions for customers. When the vehicle arrived in the UK I noticed a few little cosmetic issues. It's a 21 year old car so it wasn't going to be mint condition. The side skirts are cracked on each corner and the sealant is failing. The front grill on the bonnet/hood isn't secured very well, mounting studs are missing. Both minor things, but again, it would have been nice to be told. During a Facebook Live walk around video of the vehicle, he mentioned it has a front Whiteline anti roll bar/sway bar. While on the inspection ramp, I noticed the stock item has been installed. When first questioned, his response was "the ARB? Switched? Since when, it never had them". Since sending video and photo evidence I've not received a response. I'm probably being over critical of the overall condition of an old car, but all I wanted was honesty (which he claims to have). I'm aware I wasn't his only customer, he's busy doing XYZ but other reviews praise him for great communication with regular updates and photos, I felt I didn't receive the same treatment. 
    • I was able to get some underside photos while the car was on the ramp The suspension is all Altezza/IS200/IS300 so getting part's will hopefully be less of a headache
    • Welcome to my 2004 Toyota Mark ii IR-V Fortuna (series 2) With a 1JZ-GTE powerplant under the bonnet (hood) it'll give me plenty of scope for power upgrades. For those who aren't familiar with imports, the 1JZ-GTE is a 2.5L 6 cylinder VVTi engine with a single turbocharger. This has the factory R154 5 speed gearbox, along with a aftermarket 2 way LSD differential (brand unknown). Under the arches are a set of CST Zero 1 alloys, 18x9 +30 225/40 up front and 18x9.5 +15 265/35 on the rear. The car was quite low in Japan and there's evidence of the wheels catching the rolled arches/fenders. The tyre's aren't great so I'm in two minds whether to replace both or just the tyres and put up with the wider wheels on the rear. The car still uses stock brakes with the addition of some braided hoses. The exterior is stock with the exception of a BN Sports front bumper and a replacement Fortuna grill  Moving to the interior, the steering wheel has been replaced with a dished MOMO steering wheel (which will get swapped for my Momo Tuner for the time being) Defi Link Gauges are mounted above the climate controls and on the A pillar, the Oil Temp,Oil Pressure,Water Temp and Boost gauges should help with spirited and track driving  The stock seats have been replaced with some retrimmed Recaro bucket seats. Being a larger build these are a little snug, unfortunately the orange isn't for me so I'll look into replacing these down the line. Other modifications include a twin plate clutch, Blitz intercooler, Evolve alloy radiator, a stainless exhaust with decat, HKS EVC-S boost controller and coil overs
    • Apologies for the long read My R34 GTT was up for sale at the beginning of spring due to a few repairs creeping up. The strut tops needed replacing, roof and bonnet (hood) painting (yay for 3 stage pearl) and the underside stripped and treated. I sold the car which allowed me to be in a much better place financially. Leading up to the sale I was already thinking about the replacement. In an ideal world it needed to be a good all-rounder. Something I can mess around with, modify, do track days, do the school run, go on long drives etc.  Options included but not limited to... Laurel C35, Evo 8/9, Civic FD2, Impreza Hawkeye, Aristo and even an Audi S4 Avant (I've already got the Mazda 6 wagon). But there was always one car at the top of the list The Toyota Mark ii JZX110 I found an advert on a Facebook group for an example in Japan, from a seller called Jon at Rising Sun Exports. A few messages back and forth and Jon calls me from Yokohama one morning (or afternoon in his case). He briefly explained the import process, the costs involved and a repeat of the advert. After much deliberation, the price was agreed and the sale was locked in. I've never imported a vehicle so I jumped into the unknown head first. The money transfer was completed through wise.com (fees apply), very easy to use and the money was with him within a day or two.  The car suspension was raised for the vessel and the car dropped off at the port. It was 7 weeks later when the bill of lading was received and the freight invoice sent to me, followed by the export certificate a couple of days after (both digital copies) In the mean time the port had been in contact. I needed an agent to deal with the NOVA (notification of vehicle arrival) along with the tax/duty invoice, this was £75.00. The port also had a fee of £100, I'm guessing to cover the cost of the 10 day 'free storage' and for moving the car off the boat etc. They need a copy of the vehicle invoice, freight invoice and export certificate to allow the vehicle to pass through customs. The vessel arrived on Tuesday 5th August, the tax/duty invoice was generated and sent over. This is generally tax 20% and duty 10% of the vehicle value. Although the invoice came in at a higher amount than I had calculated. Once HMRC had received the payment the vehicle could be released from customs. I thought once the tax/duty was paid you could collect at any point, that's not the case. Your agent will need to book a collection slot, I requested Thursday 7th which was accepted, with a 9:00am slot allocated. It was a 5:00am start from Norfolk heading to Southampton. We eventually found the compound, upon presenting the bill of lading and some ID they released the car (they drove it out of the compound to the front ready for us to load up). The email from the port stated each slot had a 10 minute window, which seemed abit farfetched but the staff said it's not a strict rule. We were there for approx. 30-40 mins in total. A week prior to collecting I contacted my garage and explained the situation, I was able to get an inspection slot that afternoon. For the registration, DVLA require the car to be insured, for this I used a company called Adrian Flux who can insure the vehicle using the VIN number. 
    • Hey guys, looking for these side skirts if anyone can help me out. 
×
×
  • Create New...